Most Recent Weekly Report: 5 December-11 December 2012

Based on analyses of satellite imagery, the Darwin VAAC reported that an ash plume from Langila rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 110 km NW on 5 December. Elevated sulfur dioxide concentrations were also detected.

Most Recent Bulletin Report: February 2010 (BGVN 35:02)

Weak ash plumes in February 2010

In September 2009 eruptions occurred at Langila's Crater 2, sending aloft dense ash plumes seen for hundreds of kilometers. Activity subsided but continued as late as the end of October 2009 (BGVN 34:11). Later reports from the Rabaul Volcano Observatory noted activity at Langila in December 2009 and February 2010. No MODVOC thermal alerts were recorded after 5-6 October 2009, through February 2010.

Vulcanian eruptive activity continued at Crater 2 throughout December 2009. The eruptive activity consisted of variable gray ash clouds on most days of the month that rose ~ 1 km above the summit before being blown NE, causing fine ashfall downwind.

During 11-15 February 2010 observers saw weak ash plumes from Crater 2. During the latter part of the month the plumes were stronger, rising 700-900 m above the crater and drifting SE and SW. During 15-19 February observers heard occasional weak booming noises.

Weekly Reports

5 December-11 December 2012

Based on analyses of satellite imagery, the Darwin VAAC reported that an ash plume from Langila rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 110 km NW on 5 December. Elevated sulfur dioxide concentrations were also detected.

Based on analyses of satellite imagery, the Darwin VAAC reported that on 30 September an ash plume from Langila drifted 260 km NW at an altitude of 4.3 km (14,000 ft) a.s.l. On 5 October, a diffuse ash plume rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 185 km N.

RVO reported that emission of ash and white vapor plumes from Langila's Crater 2 continued during 1-16 October. Plumes rose to altitudes of 1.8-2.8 km (5,900-9,200 ft) a.s.l. and drifted WNW. The emissions were occasionally accompanied by roaring noises. Crater 3 was quiet.

Source: Rabaul Volcano Observatory (RVO)

26 September-2 October 2007

RVO reported that emission of ash and white vapor plumes from Langila's Crater 2 continued during 1 August-30 September. Ash plumes rose to altitudes of 1.8-3.3 km (5,900-10,800 ft) a.s.l. and drifted WNW. The ash emissions were occasionally accompanied by roaring and booming noises. On 8 August, a large explosion produced an ash plume that rose to an altitude of 5.3 km (17,400 ft) a.s.l. and drifted SW. Ashfall was reported in areas downwind. Incandescent fragments were ejected from the summit on 21 and 22 September. Crater 3 was quiet.

Source: Rabaul Volcano Observatory (RVO)

11 July-17 July 2007

RVO reported that emission of ash plumes from Langila's Crater 2 continued during 6-7 and 9-13 July. Ash plumes rose to an altitude less than 2.3 km (7,500 ft) a.s.l. and drifted N and NW. Crater 3 was quiet.

Source: Rabaul Volcano Observatory (RVO)

4 July-10 July 2007

RVO reported that emission of ash plumes from Langila's Crater 2 continued during 10 June-3 July and were occasionally forceful. Ash plumes rose to altitudes of 2.3-3.3 km (7,500-10,800 ft) a.s.l. and drifted N and NW. Crater 3 was quiet.

Source: Rabaul Volcano Observatory (RVO)

6 June-12 June 2007

RVO reported that the emission of ash plumes from Langila's Crater 2 continued during 1-10 June and were occasionally forceful. Ash plumes rose to altitudes of 2.3-4.3 km (7,500-14,100 ft) a.s.l. and drifted NNW. Ashfall was reported at Kilenge Catholic Mission (about 10 km NW of the volcano) and surrounding areas. The emissions were continuous on 6, 7, and 10 June and accompanied by roaring noises. Booming noises were heard on 1 and 10 June. Crater 3 was quiet.

Source: Rabaul Volcano Observatory (RVO)

30 May-5 June 2007

RVO reported that the emission of ash clouds from Langila's Crater 2 continued during 22 May-1 June and were occasionally accompanied by roaring noises. Two large explosions on 30 May produced ash plumes that rose to an altitude of 5.3 km (17,400 ft) a.s.l. and drifted NW. Ash plumes rose to altitudes of 3.3-4.3 km (10,800-14,100 ft) a.s.l. and drifted NW during 22 May-1 June. Ashfall was reported from Kilenge Catholic Mission (about 10 km NW of the volcano) and surrounding areas during the last few days of May and 1 June. Incandescence was visible on 29 and 31 May. Crater 3 was quiet. Based on observations of satellite imagery and information from RVO, the Darwin VAAC reported that an ash plume rose to an altitude of 3 km (10,000 ft) a.s.l. on 3 June and drifted W.

RVO reported that emission of ash clouds from Langila's Crater 2 continued during 23 February-9 March. Incandescence was visible on 24 and 25 February and 6 and 8 March. Plumes rose to less that 2.3 km (7,500 ft) a.s.l. and drifted SE during 7-9 March.

Source: Rabaul Volcano Observatory (RVO)

21 February-27 February 2007

On 13 and 14 February, eruptive activity at Langila's Crater 2 consisted of continuous emissions of gray ash plumes. During 15-23 February the emissions became forceful. Plumes rose to an altitude of 2.3 km (7,500 ft) a.s.l. and drifted SE and SW. Occasional roaring noises were heard accompanying emissions. Incandescence was observed at the summit.

During 2-20 November, eruptive activity at Langila's Crater 2 consisted of continuous emissions of pale gray ash plumes that rose to an altitude of 2.3 km (7,500 ft) a.s.l. and drifted N, NW, and W. On 6 November, two explosions produced ash plumes that rose to an altitude of 3.8 km (12,500 ft) a.s.l. Explosions of incandescent lava fragments were visible during 2-6 November and roaring noises were heard on 2-6, 12-16, and 20 November. Incandescence from the crater was visible intermittently during the reporting period.

Source: Rabaul Volcano Observatory (RVO)

1 November-7 November 2006

During 1-2 November, eruptive activity at Langila's Crater 2 consisted of continuous emissions of pale gray ash plumes that rose to an altitude of 2.3 km (7,600 ft) a.s.l. and drifted N. On 1 November the plumes were accompanied by forceful white vapor plumes, and roaring noises were heard at regular intervals. Explosions of incandescent lava fragments were also visible.

Source: Rabaul Volcano Observatory (RVO)

25 October-31 October 2006

During 23-31 October, eruptive activity at Langila's Crater 2 consisted of continuous emissions of gray-to-brown ash plumes accompanied by sub-forceful gray ash plumes. Pilots reported plumes to an altitude of 2.4 km (8,000 ft) a.s.l. that drifted NE. Explosions of incandescent lava fragments were visible during 23-30 October. Based on satellite imagery, the Darwin VAAC reported that on 31 October a small ash plume rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted NNE.

According to the Darwin VAAC, the RVO reported that Langila erupted at 1130 on 17 October. Satellite imagery from 1133 showed no activity over Langila, but a "low level plume" was visible farther W over Ritter Island.

During 16 February to 31 March, low-level Vulcanian activity continued at Langila's Crater 2. Eruptive activity was characterized by low-energy emissions of diffuse pale gray ash between 30 January and 7 February. Activity changed to subcontinuous forceful emissions of dark gray ash on 1, 2, 6, 7, and 9 March. The resultant plumes did not rise higher than 2 km above the summit crater (or 10,900 ft a.s.l.) before drifting WSW of the volcano. Weak-to-bright glow and weak projections of incandescent lava fragments were visible on 22, 23, and 28 February, and on 1, 2, and 6 March. There was no activity at Crater 3.

Vulcanian eruptions continued at Langila's Crater 2 during 21-27 November, with a slight increase in the level of activity compared to the previous week. The activity increase was marked by ash emissions that rose to heights between 1 and 2 km above the summit crater (or 7,650 and 10,900 ft a.s.l.). The ash clouds drifted W, SW, SE, and NW, depositing ash in those areas. Incandescence and projections of volcanic material were visible at the volcano during many nights. Crater 3 was quiet during the report period. Seismicity was at low-to-moderate levels, consisting of low-frequency earthquakes associated with the Vulcanian activity and periodic volcanic tremor.

During 12-18 September, Langila's Crater 2 continued to forcefully erupt ash at irregular intervals. The resultant ash plumes drifted NW and W. Incandescence and weak projections of volcanic material were visible on the evening of 13 September. There was no activity at Crater 3. Seismicity was at low levels at the volcano, consisting mainly of low-frequency earthquakes.

Source: Rabaul Volcano Observatory (RVO)

24 August-30 August 2005

RVO reported that during 22-28 August, modest eruptive activity was observed at Langila's Crater 2. Occasional forceful emissions of ash produced plumes that rose ~1 km above the crater (or 7,600 ft a.s.l.) on 22 and 25 August, but reached only several hundred meters after that. The ash plumes drifted N and NW resulting in fine ashfall in downwind areas, including the town of Kilenge. Seismicity was at low levels, consisting mainly of low-frequency earthquakes. The Darwin VAAC reported that a plume was visible on satellite imagery on 30 August extending NNW.

RVO reported that moderate levels of volcanic activity occurred at Langila's Crater 2 during 15-21 August. The activity was marked by occasional sub-continuous forceful emissions of ash. The resultant ash clouds rose as high as 1 km above the volcano (or ~7,600 ft a.s.l.) before drifting N and NW and depositing fine ash in villages along the island's coast. On the evening of the 18th, strong projections of incandescent lava fragments were seen. During the report period, there was no activity at Crater 3 and seismicity was low at the volcano. Based on a pilot report, the Darwin VAAC reported that ash from Langila was visible on 23 August at a height between 3 and 4.6 km (10,000 and 15,000 ft) a.s.l. No ash was visible on satellite imagery.

According to the Darwin VAAC, low-level ash plumes emitted from Langila were visible on satellite imagery during 8-13 June. RVO reported to the Darwin VAAC that fluctuating, moderate eruptive activity was expected to continue at the volcano.

The International Federation of Red Cross and Red Crescent Societies (IFRC) reported that eruptive activity occurred at Langila on 2 June with more ash than normal being emitted from the volcano. Prevailing winds carried most of the initial ashfall to the sea, but lower-level winds redirected the ash back onto the island. About 10,000 people live near the volcano and there were reports of increased cases of respiratory problems and eye irritation. During an aerial inspection of the area on 6 June, IFRC determined that ~3,490 people had been affected by the eruption, mainly in the villages of Aitavala, Masele, Kilenge, Ongaea, Potne, and Sumel, but also to a lesser extent in Vem, Galegale, Tauale, and Laut. Ashfall damaged small food gardens and contaminated some water sources. The provincial government encouraged voluntary evacuation of affected areas.

Between 28 April and 4 May sub-continuous forceful emissions of thick white to gray ash-laden clouds rose about 700-800 m above the summit crater. Glow was visible during night; projections of incandescent lava became frequent during the latter part of the period. On the afternoon of 4 May the emissions changed to dark ash clouds and there were explosions with booming noises. A thin plume from the 4 May activity was seen on satellite imagery extending over 100 km NW. Very bright glow was visible during the night with moderate projections of incandescent lava fragments. Reports received by mid-day on 5th indicated the activity to be continuing. A lava flow was also produced. Light to moderate ashfall was reported to the NW at Kilenge.

Based on information from RVO, the Darwin VAAC reported that ash emissions from Langila rose to ~2.1 km (~7,000 ft) a.s.l. on 3 May. A very small plume and a hot spot were visible on satellite imagery.

Based on information from a pilot report, the Darwin VAAC reported that on 11 July at about 0900 an ash cloud from Langila was observed at a height of ~3.4 km. No ash was identifiable on satellite imagery.

Bulletin Reports

All information contained in these reports is preliminary and subject to change.

07/1973 (CSLP 96-73)Lava emission from Crater 3 in mid-July

Card 1681 (20 July 1973) Lava emission from Crater 3 in mid-July

The eruption of lava from the No. 3 crater . . . commenced on 12 July 1973. There had been increased ash and steam emission during the preceding month. The lava flow was approximately 1 km long and 300 m wide by 18 July with lava still being extruded accompanied by loud rumblings. Only two other flows have been recorded this century, in 1960 and 1967. Both of these were small.

"Activity since the previous event report consisted of slow, steady lava flow from Crater 3 for about six months from July 1973. This has apparently now ceased, although minor explosive activity occurring throughout this phase still occurs. A few soft ash ejections from Crater 2 occurred during this phase."

"Last year's mild Strombolian eruption at Crater 2 [NE crater] (figure 1 and 2) ended in mid-December, after a peak in early September during which a small amount of lava rose into the crater without overflowing. A new inner crater was blown through this lava a few weeks later and seems to have become considerably enlarged between aerial inspections on 21 March and 18 May. An unusually thick column of white vapor has been issuing from this crater during the last few weeks and a number of explosions were reported during May. A new mild Strombolian eruption [but see 3:9] from Crater 2 began 27-28 May and is continuing."

Figure 1. Sketch map of the NW tip of New Britain Island, showing Langila volcano and surrounding features. The portion of Langila's summit outlined by a box is shown in detail in figure 2. After Johnson and others (1971).

Figure 2. Summit area of Langila in 1970; the area shown is outlined in figure 1. From Palfreyman and others (1981).

"An eruptive phase which began in late April and intensified markedly in late May has continued to the present (25 September). However, a volcanological party observed the activity from 30 May-9 June and found that it was not Strombolian as suggested by early reports, but Vulcanian in character. Typically, one or two larger explosions occurred per day, with a number of lesser ones. A lull was noted during mid-July and from late August. Since the first week of September, there has been little activity."

The character of activity changed in late October, after six strong explosions had occurred earlier in the month. Explosions became more frequent, but only a little ash was present in the eruption clouds. Ash contents increased on 27 November and remained high through December while frequent explosions persisted. Since 27 November, a gray ash plume has been continuously visible over the volcano.

Aerial inspections on 7 and 15 December revealed an active lava dome in Crater 2 (Langila's NE crater). Incandescence was visible in the dome's surface fissures during these (daytime) overflights. Glow could be seen at night from 10 km away on 13 and 21 December.

Frequent ash ejection continued through January. Aerial inspections on 4, 15, and 29 January showed that the lava dome discovered in December has risen to the rim of Crater 2 without overflowing. By the end of January, a new craterlet had formed in the fresh lava surface.

"For most of September the activity consisted of weak vapour emission accompanied by occasional small explosions. Only a very little ash was emitted. On 27 September a series of 10 loud explosions was accompanied by the emission of a dense ash cloud. A heavy ashfall occurred at Kilenge mission, 10 km NW of the volcano. No further details are yet available."

"No further strong explosions have been observed since those of 27 September. The ash deposit from the 27 September explosions was several millimeters thick 10 km from the source. Grey ash clouds were seen on a few days at the beginning and end of October, and white vapour emissions were observed occasionally. Seismic activity remained at a low level."

"A new crater was formed on the flank of Crater 3 on 19 January. Moderately thick brown/grey ash was explosively ejected until 20 January. Weak-moderate ash emissions resumed 24 January and continued intermittently until 29 January. Incandescence and rumbling were observed 28 January.

"During an overflight 28 January a brown-coloured deposit was observed extending up to 600 m from the new vent. Seismic activity consisted of numerous discrete volcanic events and possibly periods of tremor."

"Sometime between overflights on 28 January and 15 February, effusion of lava commenced on the upper W flank of Crater 3, from the new vent formed on 19 January. When first observed on 15 February, the flow was about 700 m long. Explosions and rumbling were heard throughout the month, and glow and lava fragment ejections from the new vent were seen occasionally. Little ash emission was observed, but blue and white emissions were common. Crater 2 emissions consisted solely of white vapour.

"The seismograph was shifted from Kilenge Mission (10 km W of Langila) to Cape Gloucester airstrip (8 km N of the volcano) to enable joint direct visual and seismic observations. Seismic activity associated with the eruption was weak, consisting of tremor-like signals and probable explosion events."

"Langila's eruption continued but observations have been prevented at times by poor weather. Incomplete reports for March indicated that incandescent explosive activity was continuing in the new crater, formed on 19 January. Blue and white vapour emissions from the new crater were commonly observed in April. Brown ash emissions were seen 9 and 10 April, and at night on those dates incandescent lava fragment ejections occurred. Crater glow was seen occasionally during the month, and rumbling and explosion sounds were heard daily. The 1980 lava flow appeared to have grown little since it was first seen on 15 February. Crater 2 usually emitted white vapour, and brown emissions were reported on 2 days in April. Explosive activity was expressed seismically as small discrete events that had the appearance of discontinuous tremor."

"The eruption continued at moderate to low intensity. From the observation post about [10] km away, roaring, rumbling and detonations, were heard almost incessantly. Small Vulcanian explosions were occasionally observed from the active vent in Crater 3 (formed on 19 January).

"During a ground inspection on 8 May, detailed observation of several explosions revealed that blocks were commonly ejected to a height of about 600 m, accompanied by loud roaring. The concluding stages of explosions were characterized by streaming of translucent vapour followed by conspicuous emission of blue vapour. A larger explosion on 9 May produced a small base surge which travelled about 300 m W, leaving a pale brown deposit.

"The 1980 lava flow is blocky, and similar in hand specimen to lavas produced in the 1970's. The lava flow had ceased moving, and its length was about 800-1,000 m. Since it was first observed in February, three distinct lobes have entered adjacent valleys, the E lobe being the longest. A preliminary estimate of flow volume is 3 x 105 m3."

"Eruptive activity continued apparently without change during June. Light grey explosion clouds were occasionally observed rising from the active vent in Crater 3. Steady glow from this vent was observed on 5 June. Seismicity continued at the same intensity as previously."

"Vulcanian explosions continued in July from the active vent at Crater 3, and crater glow was seen on several nights. Eruption clouds were usually brown/grey, but otherwise emissions were white and rarely blue. Emissions from Crater 2 were usually white, but possible ash contents in the emissions were reported on several days. Weak glow from Crater 2 was reportedly observed on one occasion. The level of seismic activity remained steady, and consisted of moderate-amplitude volcanic earthquakes, probably of explosion origin."

"The eruption continued at the same intensity in August. Emissions from the active vent in Crater 3 were mostly white and blue, but during a more active phase at mid-month grey emissions were observed. Lava fragment ejections and glows were observed on four consecutive nights 14-17 August. Rumbling and explosion sounds were heard on most days during the month. Crater 2 usually emitted white vapor, but on four occasions in the first half of August, brown emissions were observed. Glow at Crater 2 was observed on 4 August. The level and character of seismic activity was unchanged."

"Observations of glow and lava fragment ejections from the active vent at Crater 3 were more numerous than in previous months. White and blue vapours were the common emission products, but grey emissions were seen on several days in the second half of September. Rumblings were heard throughout, occasionally augmented by explosive sounds. Occasional brown or grey emissions from Crater 2 were observed, but usually this vent released only white vapours. Seismic activity was reportedly unchanged."

"Langila was inspected between 1630 on 28 October and [0915] on 29 October, following reports of increased activity. Large Vulcanian explosions took place from Crater 2 at intervals of several minutes or more and produced dark grey convoluting ash clouds reaching heights of 3-5 km. Minor ejections of incandescent lava fragments also took place, producing impact craters to a distance of at least 200 m. Crater 3 contained a body of plastic incandescent lava that was upheaved frequently by Strombolian explosions. Incandescent lava fragments were ejected to 300 m in horizontal distance. The crater was topped by a pale grey emission cloud. A blocky lava flow [first noticed on 13 October] had advanced about 2 km on a broad front from Crater 3. The lava looked similar to previous flows, which have consisted of low-silica andesite. Seismic activity (volcanic tremor and B-type events) was greatly intensified in October, necessitating an increase in seismograph attenuation of 18 decibels."

"Intensified eruptive activity that began in mid-October (05:10) continued until 8 November. Dark emission clouds continued to be released from Crater 2, and emission clouds from Crater 3 were pale grey. Ejections of incandescent lava fragments from both craters were accompanied by rumblings and explosion sounds. The lava flow from Crater 3 was reported to be still active on 11 November.

"A decline in the intensity of the eruption was evident on 8 November, when seismograph attenuation was reduced by 18 decibels. However, glows and ejections of incandescent lava fragments continued from both craters, and grey ash and vapour clouds continued to be emitted."

"Vapour emissions continued from Craters 2 and 3. Some small ejections of brown-grey ash rose from Crater 2. The lava flow from Crater 3 was still active and had almost reached the terminus of the 1975 flow."

"The first 3 months of 1981 have shown a steady decline of eruptive activity. Occasional brown ash-laden emissions from Crater 2 were observed in January, but in February and March emissions from Crater 2 were white and apparently of declining volume. Crater 3 released blue and white vapours in January and February; in March only small volumes of white vapour were emitted. The last time glow was observed was on 21 January from Crater 2. Seismic activity from Langila was at a low level January-March. Small tremor-like signals continued to be recorded."

"Eruptive activity, which had been declining since a peak in October 1980, increased in April. Explosions from Crater 2 produced dark ash clouds on 13 and 29 April. Weak glow above this crater was seen on 25 and 26 April. Pale grey emissions from Crater 3 were observed on 2, 14, 16, and 17 April. Blue emissions from the same vent were noticed on 8 days. No explosive sounds were detected at the observation post about 10 km away. The intensity of seismic activity remained low."

"On most days of observation, Crater 2 emitted white vapour, and brown or rarely grey ash in moderate volumes. Crater 3 released small volumes of white, blue, and occasionally grey emissions. No glows or lava fragment ejections from either crater were observed, and no volcanic sounds were heard."

"A further intensification of activity took place in June. Moderate to strong white and brown emissions from Crater 2 were commonly seen. Ashfalls were reported on several days from locations about 10 km from the volcano. Rumbling and/or explosive sounds were heard on most days. Crater glow or ejections of incandescent lava fragments from Crater 2 were seen on five days in the second half of the month. Crater 3 was less active, commonly releasing white or blue vapours, but weak grey emissions were occasionally seen. Seismic activity strengthened considerably. Large-amplitude, multiple explosion-type earthquakes and prolonged periods of tremor clearly represented tephra explosions and bouts of gas venting at Crater 2."

"Vulcanian explosions occurred at Crater 2 throughout July. Explosion and rumbling sounds were heard at an observation post about 10 km N of Langila. Brief aerial inspections on 16 and 20 July revealed that eruptions at Crater 2 were taking place at intervals of about 10 minutes. The maximum height reached by the eruption clouds was probably about 300-400 m. Glow from Crater 2 was seen on four consecutive nights, 25-28 July. Crater 3 was less active, usually releasing white and blue vapours in small volumes, but grey emissions were occasionally seen.

"The overall level of seismic activity intensified near the end of July, but its character remained similar to that observed in June. Periods of strong tremor were generated by explosions and prolonged gas jetting at Crater 2."

"Eruptive activity at Crater 2 declined near the middle of August; frequent Vulcanian explosions and periods of ash emission gave way to white and blue vapour emission occasionally punctuated by intervals of brown or grey ash emission. Ashfalls were noted at coastal locations about 10 km N and NW of the volcano until 14 August. Ejections of incandescent material were seen on 6, 7, 8, and 14 August. Sounds of detonations, rumbling, and roaring were heard during the first half of the month. Crater 3 released white vapours throughout August, and blue emissions were seen rarely in the second half of the month. Seismic activity declined from a peak reached near the end of July, but the character of the activity was unchanged."

"Ash emission from Crater 2 resumed near the beginning of September after about two weeks of mainly white and blue vapour emission in late August. Significant ashfalls occurred W and N of the volcano, particularly in the first three weeks of September. Glow and ejections of incandescent lava fragments from Crater 2 were occasionally observed, and rumbling and explosion sounds were heard throughout the month. Crater 3 activity continued to be weak, consisting of weak emissions of white vapour.

"Seismicity fluctuated in strength. Several seismic events had the appearance of Vulcanian explosion earthquakes (from Crater 2), but the main feature of the seismicity in September was prolonged periods of discontinuous tremor, probably representing periods of ash emission. Frequent small brief seismic events began to be recorded at mid-month."

"Eruptive activity intensified in October when Crater 3 became strongly active, emitting incandescent tephra and a new lava flow. After a brief interval of ash emission on 3 October, Crater 3 began a sustained period of explosive activity on 9 October. Ejections of incandescent tephra were seen on 15 October and continued from 17 October throughout the month. The production of a new lava flow from Crater 3 was suspected on 27 October and confirmed on the 28th. The flow rate was apparently low.

"Activity at Crater 2 may have declined since late September. Vulcanian explosions occurred at intervals of several days, and periods of less-explosive ash emission were observed at the beginning and end of October. At other times, Crater 2 released white and blue vapours. Crater 2 glow was observed on 1, 3, 17, and 18 October.

"Ashfalls were reported in inhabited areas about 10 km N and W of the volcano on about 50% of days during the first half of October. Seismicity remained at a fairly low level, consisting mainly of numerous small events probably originating from Crater 3."

"Strong eruptive activity continued in November. The present eruptive episode is the most intense since October-November 1980 (05:10-11). Detailed observations were made by a volcanologist 17-26 November.

"Crater 2 produced a wide variety of activity. Vulcanian explosions rising to about 2 km were commonly observed. Frequency of explosions varied from minutes to hours, and periods of near-continuous (Strombolian) activity were also noted. Crater 2 glow was seen during the first half of the month, followed by apparently more intense activity including ejections of incandescent tephra occasionally rising to 0.5 km above the source. Commonly the larger Crater 2 explosions registered a seismic airwave. Rumbling and detonations from Crater 2 were heard throughout the month.

"Small nuées ardentes were produced by backfall of ejecta from some of the Crater 2 explosions. The largest of the nuées travelled about 2 km down the E flank. Periods of continuous harmonic tremor appeared to be related to resonance effects in the Crater 2 lava conduit. Continuous fluctuating glow, incandescent tephra ejections, and associated rumbling and booming sounds were noted from Crater 2 during some of the periods of harmonic tremor.

"Crater 3 activity may have declined during the month. Incandescent tephra ejections or crater glow were common during the first half of the month, but only occasionally observed later in November. Several large Vulcanian explosions were observed. One on 13 November was reported by a passing aircraft pilot as rising to about 6-7 km altitude, and having a columnar appearance. Crater 3 eruptions later in the month were often single events. Some were accompanied by loud detonations and others were soundless. Some of the soundless eruptions were registered seismically as large-amplitude, low-frequency events.

"The new lava flow from Crater 3 appeared to become inactive in mid-November. The flow rate was evidently low, as only a small volume of lava was extruded during the 2-week period of lava effusion."

"Strong eruptive activity continued during December although a decline was apparent in the last week of the month. Activity was centred at Crater 2, which produced dark brown or dark grey tephra emissions throughout December. On several days in the first half of the month the emissions were reported as being thick. Significant ashfalls at inhabited areas about 10 km to the N and W occurred 6, 8-12, 14, 17, 22, and 29 December. Sounds of explosions and rumbling were heard 1-14 December, and detonations were frequent 9-10 and 15-17 December. Incandescent tephra ejections or crater glow were seen 1-4, 8, 13-18, and 20 December. Dark emissions from Crater 3 were observed once (on 1 December); otherwise, the only products from this crater were white and blue vapours. Seismic activity showed a good correlation with visible activity. Periods of stronger visible activity were usually accompanied by large-amplitude volcanic earthquakes and periods of harmonic tremor."

"Occasional Vulcanian explosions from Crater 2 were reported. One explosion on 11 January was accompanied by a loud detonation, and an associated earthquake was felt 10 km away. Crater 2 glow was seen on 14 and 16 January.

"From 1-17 January, Crater 3 produced white and blue emissions. From the 18th pale grey Strombolian eruption clouds were seen. Rumbling and explosion sounds were associated with these eruptions. Crater 3 glow or ejections of incandescent tephra were seen beginning then. An active lava flow from Crater 3 was first observed 21 January.

"Both craters produced occasional Vulcanian explosions during February. Activity appeared to be stronger in the first half of the month. Explosions from Crater 3 rose to 3-4 km on 9 and 11 February, and from Crater 2 to 6-7 km on the 13th and 14th. Glow and incandescent tephra ejections were observed at Crater 2 most nights the first half of the month, occasionally the second half. At Crater 3 incandescent tephra emission was reported only on 7 February.

"The main feature of February seismicity was the registration of several Vulcanian explosion earthquakes per day. Larger events were recorded 8-17 February. Two periods of frequent, brief, small-amplitude seismic events occurred 6-9 and 13-16 February. This activity became more intense on the 14th and 15th, giving rise to signals resembling discontinuous seismic tremor."

"A fairly low level of activity prevailed in early March, but in the second half of the month activity at both craters intensified. Crater 3 erupted incandescent tephra 18-22 March, accompanied by frequent explosive detonations and loud rumbling. From 22 March until the end of the month glow and incandescent tephra ejections from Crater 2 were seen on most nights. Dark eruption clouds were occasionally seen, and loud explosions and rumblings were heard. Seismicity was stronger from 18 March, and correlated with the intensified visible activity."

"A steady level of mild eruptive activity prevailed at Crater 2 during the first part of April. Distinctly stronger activity was evident on the 23rd. Eruption clouds became more heavily charged with tephra, audible explosions more intense, and ejections of incandescent lava more frequent. Activity at Crater 3 was subdued, consisting usually of weak emissions of white and rarely grey vapour, and occasional emissions of blue vapour. Relatively small explosions producing dark brown or grey tephra clouds were observed on 15 and 26 April. Ashfalls at the observation post, about 10 km N of the craters, occurred on 15, 20, 25, and 30 April. Seismicity was steady at moderate to low levels during the first half of April, but intensified on the 20th. The increased seismicity was directly associated with the stronger visible explosive activity at Crater 2."

"Following a period of moderately intensified explosive activity from Crater 2 in the second half of April, strong eruptive activity took place from this vent 2-16 May. During peak activity, 5-9 May, strong Strombolian activity was observed. Frequent ejections of bright red incandescent lava to maximum heights of 250-300 m above the crater were seen. An eruption column rose to about 4 km on 6-7 May. Ashfalls were experienced in inhabited areas about 10 km N and NW of the volcano during most of the first half of the month. The total thickness of these deposits was probably several millimeters.

"A significant event in this phase of Crater 2 activity was the production of a substantial lava flow. Several lobes developed NE of the crater, the largest extending to about 1 km in length. The volume of the flow is estimated to be 0.5-1.0 x 106 m3. Occasional Vulcanian explosions took place 17-31 May at Crater 2, and crater glow was seen once, on the 19th. Throughout the month Crater 3 emitted white and blue vapours at a low rate.

"Seismicity corresponded closely with the intensified visible activity. During the peak eruptive period seismic tremor was produced by the Strombolian explosive activity. As eruption intensity waned, discrete earthquakes associated with Vulcanian explosions at Crater 2 became prominent."

"Following a strong eruption from Crater 2 in early May, activity declined sharply. From about 17 May occasional Vulcanian explosions took place at this crater, but usually the only emissions were white vapours and occasionally blue vapours in small volumes. Ashfalls were reported 10 km N of the crater at the beginning of June and on 8, 10, and 31 July.

"Crater 3 has shown declining activity since April when occasional explosions were seen. Weak white and blue emissions were seen until about mid-June, but since then the crater has been completely inactive except for weak white vapour emissions on 18 July. Seismic activity has remained low since mid-May."

"A resurgence of activity was evident in August as Vulcanian explosions from Crater 2 became more common. Explosive eruptions occurred on 5, 12, 14, 15, 17, 24, and 31 August, and light ashfalls were experienced at the observatory post 10 km to the N after most of these eruptions. The cloud from the largest explosion, on 15 August, reached a height of about 6 km. Crater 3 continued to show little or no activity. Seismic activity generally remained low, although earthquakes associated with the Vulcanian explosions were recorded."

"Activity in September was similar to that seen in August. However, Crater 2 showed a more intense phase of activity in the second half of the month which included more frequent Vulcanian explosions and periods of continuous ash emission. Light to moderate ashfalls at the observation post 10 km N of the volcano were recorded on 5 days but mostly in the second half of the month. No crater incandescence was seen. Blue vapour emissions from Crater 2 were observed on several days at the beginning and end of the month.

"Crater 3 showed little or no activity apart from weak emissions of white-grey vapour. The greyish color is not considered to be caused by entrained ash but to be an effect of peculiar light conditions [during early-morning periods of observation].

"Seismicity was generally at a low level, although explosion earthquakes were associated with the Vulcanian activity at Crater 2."

"The level of activity in October was similar to that observed in September. Grey and brown ash emissions from Crater 2 were seen on about 50% of days; otherwise, white vapours were emitted. Ashfalls in areas about 10 km from the volcano were reported on 4, 5, and 6 October. Vulcanian explosions were observed on 7 and 30 October. On the 7th a dark brown eruption column rose to about 3.5 km, and incandescent ejecta started fires in vegetation at the foot of the volcano. The explosion on the 30th was much smaller, the ash column rising only a few hundred meters. Crater 2 was more active from the 22nd. Crater glow was seen on 22, 24, and 25 October, and weak to strong rumbling sounds from the crater were heard on 22, 23, 24, 26, and 29 October.

"Crater 3 continued its low level of activity, releasing white and blue vapours in small volumes. Seismic activity remained at a low level. A few Vulcanian explosion earthquakes were recorded."

"A generally low level of activity prevailed during November, when both craters usually emitted tenuous white vapours, and usually no crater incandescence or sound effects were observed. However, two large Vulcanian explosions from Crater 2 were reported, on 12 and 22 November. A dense ash cloud was erupted at about 1930 on the 12th. Brilliant lightning displays were reported, and the eruption cloud contained incandescent tephra. On the 22nd a 3 km-high eruption column was produced by an explosion at about 0200. Light ashfalls 10 km N and W of the volcano were reported. Seismic activity was generally low, although several explosion earthquakes were recorded.

"A detailed aerial and ground inspection was carried out on 29 November. Both craters were releasing thin white and blue vapours. At the S rim of Crater 2 a strong odour of SO2 was detected. The strong eruptive activity at Crater 2 in May resulted in significant accumulation (about 100 m) of coarse red-brown tephra mainly on the W rim of the crater. Vulcanian explosions since then have reamed out a funnel-shaped crater 250-300 m wide and about 200 m deep. No vents were visible in the floor of the crater. Crater 3 was about 150 m across and shallow, and most emissions seemed to originate from sources scattered around the crater walls. The nose of the westernmost lobe of the May Crater 2 lava flow was visited. The flow thickness at that point was about 20 m."

"Activity increased in December. Crater 2 produced thick white emissions while Crater 3 released white or blue vapours. Seismicity was generally low. Vulcanian explosions of increasing violence occurred from Crater 2 on 1, 14, 16, 25, and 26 December. On these occasions, the development of a dark grey ash-laden column up to 9 km was accompanied by loud rumbling noises and explosion earthquakes, and followed by light ashfalls. On 16 and 26 December harmonic tremor accompanied the subsequent escape of gases and tephra. The large explosion on the 26th at 1400 was accompanied by vivid lightning, ejected incandescent boulders up to 2 km from the crater, and started bush fires on the NW flank of the volcano. Twenty explosion shocks were recorded over the background tremor during a 25-minute period after the eruption, and Crater 2 remained incandescent for 45 minutes."

"Volcanic activity increased markedly in January and was concentrated in Crater 2. Several Vulcanian explosions were recorded every day. The most violent, 11-14 and 22-24 January, ejected incandescent boulders and tephra, illuminating the dark ash-laden column and setting fire to vegetation on the volcano's flanks. Consecutive ashfalls were blown SE over unpopulated areas. Crater 3, meanwhile, was quietly exhaling weak white vapours. In the sub-continuous seismic background, each discrete explosion was recorded as a sharp, large-amplitude event with a period of 1.5 Hz."

"The increased Vulcanian activity of Crater 2 in January culminated in a rise of the magma column, with an eruptive phase maximum 11-16 February. The 3-11 February buildup of the eruption consisted of approximately hour-long periods of loud rumbling noises, with deep explosion sounds at 5-30 second intervals. Several times per day at irregular intervals, individual explosions produced black ash-laden columns that rose as much as 3-4 km before being dissipated by the NW winds. Night glow, observed 3 February, became more intense during this period. Low Strombolian fountaining was visible 3-5 and 9 February.

"During the six days of maximum activity, Crater 2 simultaneously displayed continuous Strombolian fountaining to 100 m and intermittent powerful Vulcanian explosions. Most of the Vulcanian explosions were laterally directed, while the continuous moderate vapour emissions and Strombolian fountaining were central and vertical, leading to the conclusion that Crater 2 may contain two more or less independent vents.

"Seismic activity consisted of a sub-continuous background of harmonic tremor and Strombolian B-type earthquakes. Each individual Vulcanian eruption produced large-amplitude low-period explosion events. The most powerful explosions occurred 12-13 and 15 February at the rate of 2-5 per hour.

"During the eruption, Crater 3 (a separate composite cone 300 m W of Crater 2) released only weak white vapours. However, the volume of emission increased to moderate or large during the first 10 days of February, the time of the activity buildup at Crater 2."

"After the increased explosive activity from Crater 2 in February, the level of activity returned to normal. White-grey vapour and ash emissions were seen on a few days, and occasional relatively small Vulcanian explosions were observed. Explosion and rumbling sounds were heard occasionally. The only volcano-seismic activity recorded was from Vulcanian explosions at Crater 2 which occurred at intervals of a few hours to about 4 days."

"A generally low level of activity prevailed during April. However, Crater 2 produced some discrete Vulcanian explosions (table 1). The explosion on the 18th was witnessed from an aircraft about 70 km away. The eruption cloud rose steadily for about 15 minutes, then began spreading at its top to become mushroom-shaped. Weak emissions of grey ash clouds were also reported on 8, 14, 20, 21, and 29 April. Crater 3 was quiet for most of the month, releasing weak white vapour, although grey emissions were reported on 21 and 26 April. On the 30th a Vulcanian explosion sent ash and vapour to a height of about 3 km. Seismic activity was generally at a low level, with occasional explosion earthquakes."

"A generally steady moderate level of Vulcanian explosive activity prevailed in May. On most days when the summit was clear, pale grey or brown emissions were reported from Crater 2. Vulcanian eruption columns rose to about 300 m on 16 May, and 7 km on 17 May. Explosion or rumbling sounds were heard on about 60% of days. Weak glow from Crater 2 was seen on 4 nights: 8, 11, 13, and 25 May. Crater 3 continued to show very mild activity, usually releasing thin white vapours and rarely emitting pale grey clouds.

"Volcano seismicity consisted of occasional Vulcanian explosion earthquakes at an average rate of several per day. On 3, 5, and 16 May explosion earthquakes were followed by periods of about 30 minutes of tremor probably produced by prolonged powerful degassing at Crater 2."

"Activity increased somewhat in June as Vulcanian explosions became more frequent. Ash emissions from Crater 2 were observed on most days and Vulcanian explosions usually occurred at rates of 0-5 per day. However, two periods of more intense activity took place; 4-17 June, and starting 26 June and continuing at month's end.

"In the first period of stronger activity, rates of recorded Vulcanian explosions reached about 30 per day on 7 June, and about 15 per day on 8 and 10-14 June. Weak red glow from Crater 2 was seen on the nights of 10 and 11 June. Light ashfalls were reported from about 10 km W of the crater.

"In the second period of stronger activity, from 26 June onwards, ash emissions from Crater 2 became more frequent, and sounds of detonations and rumbling more noticeable. Ejection of incandescent tephra was seen the night of 26 June, and continuous glow was observed early on the morning of the 27th. In the last few days of the month the volcano was obscured by the ash emissions from Crater 2. Ashfalls of several mm were reported at locations 10 km N and W of the volcano.

"Crater 3 continued to show a low level of activity, usually releasing tenuous white vapours. However, thick dark brown ash clouds were emitted on 6 June, and pale grey emissions were reported on 12 June. Volcano seismicity at Langila was dominated by the earthquakes produced by Vulcanian explosions."

"Stronger activity that commenced at Crater 2 on 26 June continued into July. During the first week of July, ash emissions blown down the volcano's flanks by strong winds occasionally obscured the active vent. A few large Vulcanian explosions were observed, and associated detonations and rumblings were heard frequently at the beginning of the month. Ashfalls continued during this period in inhabited coastal areas about 10 km to the NW and N. Weak crater glow was noted on 2 July.

"Seismic records indicate an average of about five Vulcanian explosions per day in the first week of July, accompanied by large-amplitude harmonic tremor on most days. A decline in activity was evident after 7 July as emissions became less voluminous and less ash-rich, and explosive sounds less frequent.

"Activity re-intensified somewhat from 15 July. Greater quantities of ash were ejected, resulting in renewed ashfalls in coastal areas. On a few days the volcano was again obscured by its own ash emissions. Vulcanian explosions continued to register on seismograms at an average of about 3 per day.

"A definite strengthening of Vulcanian activity at Crater 2 has been observed since late June. This phase of activity is the strongest since January-February.

"On most days in August ash-laden vapour emissions from Crater 2 were blown down the volcano's flanks by strong winds, obscuring both the active vent and Crater 3. Strong activity in the first 8 days of the month consisted of up to 15 Vulcanian explosions per day, and periods of harmonic tremor recorded 4-8 August. Light to moderate ashfalls were common in coastal inhabited areas about 10 km NW and N. A decline of activity was observed 9-20 August as emissions became less voluminous and less ash-rich, and sound effects were heard less frequently. Occasional explosion earthquakes were recorded. More frequent Vulcanian explosions, loud sound effects, and ashfalls resumed on 21 August.

"In contrast to activity in January and February 1983, when incandescent lava ejections took place, the more explosive activity at Crater 2 in August was rarely accompanied by incandescence. Weak crater glow was observed on only 2 nights (17 and 29 August). Crater 3 remained relatively inactive, usually releasing thin white vapours."

"Explosive eruptive activity continued at Crater 2, and was stronger 2-6 September. Up to 12 explosions per day were recorded, and periods of strong volcanic tremor were produced by prolonged gas venting. Activity declined 8-11 September, but re-intensified on the 12th. Moderate activity persisted for the remainder of the month, including patchy and weak tremor and 1-9 explosions per day. Weak red glow was observed over Crater 2 on 25 and 29 September. Light to heavy ashfalls were common in coastal inhabited areas about 10 km to the NW and N."

[Richard Stoiber, Stanley Williams, and Chris McKee used a COSPEC to measure the rate of SO2 emission from several volcanoes in Papua New Guinea during September (table 2). Plumes at and Manam were strong, and plume was small. Activity at Langila was weak 11 September, but had intensified during measurements the next day. The quiet-phase data were collected from the ground; all other data were acquired while flying under the plumes.]

"From the 8th until the end of the month, Crater 2 released white emissions in small to moderate quantities. However, Vulcanian explosions accompanied by loud detonation sounds and ejections of incandescent material took place on 24 and 27 October. Seismicity was at a low level 8-31 October, but rare Vulcanian explosion events were also recorded. Crater 3 released small volumes of white and occasionally blue vapours throughout the month."

"From 21-27 December, activity became much stronger, with continuous ejection of thick tephra-laden vapour to 1.8-2.7 km above the summit accompanied by continuous loud rumbling and explosion sounds. Continuous glow and ejections of lava fragments were observed at night with overflow of lava to the NE 23-28 December. This was accompanied by long periods of continuous harmonic tremor which increased in amplitude during the periods of maximum activity. Crater 3 remained inactive throughout, with only weak emissions of white vapour."

"Activity remained high at Crater 2, but Vulcanian explosions replaced the more continuous activity that produced the lava flow on the NE flank in December. For most of the time, Crater 2 produced moderate amounts of white to brown ash-laden vapour, accompanied by discontinuous rumbling and explosion sounds, while the seismic station at Cape Gloucester airstrip, 9 km away, recorded discontinuous tremors and large explosion earthquakes. Peaks of activity occurred on 7, 12, and 25 January with emission of columns of thick dark tephra-laden vapour to heights of 1.5-2.5 km above the crater. Large blocks were ejected as far as 2 km from the vent by the more powerful explosions, and ashfalls were experienced on the coast, 10 km downwind. Activity at Crater 3 was confined to the emission of white and blue vapours."

"Activity was substantially reduced during February. The main activity at Crater 2 was the release of white vapours and rarely pale grey ash clouds. One Vulcanian explosion was observed on 7 February, producing a thick dark ash cloud that rose about 3 km above the vent. Crater glow was seen on 3 and 5 February. Crater 3 continued its usual activity of weak to moderate white and blue vapour emission. Seismicity was at a low level, with only a few recorded explosion earthquakes."

"A relatively low level of activity persisted during March, although a slight intensification was noted after the 19th. Pale grey ash emissions from Crater 2 were occasionally observed 1-18 March. A strong Vulcanian explosion took place on 19 March, and on the 20th further explosions were observed. The seismic record for 20 March indicates a total of 10 explosions. A lull in Crater 2 activity was noted 21-25 March but weak ash emission began on the 26th, and explosive activity resumed on the 27th. Two or three explosion earthquakes were recorded on 27, 28, and 30 March. Crater 3 released white and blue vapours at low rates throughout the month."

"For most of April, activity was at a low level with weak to moderate white and occasionally grey emissions from Crater 2, and weak white and rarely blue emissions from Crater 3.

"However, between 7 and 17 April stronger activity took place at Crater 2. Occasional strong Vulcanian explosions producing eruption columns up to about 5 km high were accompanied by detonations and rumblings, and ashfalls were recorded in coastal areas 10 km to the N and NW. Characteristic impulsive earthquakes also accompanied these explosions."

"Activity in May was similar to that in April. Intermittent weak-moderate ash emissions from Crater 2 were reported during the first 8 days of May. During the remainder of the month Crater 2 usually released white vapours at low rates. However, strong Vulcanian eruptions accompanied by loud detonations took place on 13, 25, and 28 May. These eruptions resulted in reportedly heavy ashfalls 10 km downwind. Weak emissions of white and blue vapours continued at Crater 3."

"Activity was generally very weak at both craters in June. The emissions were usually white or occasionally blue vapours. However, lightly ash-laden clouds were emitted from Crater 2 on 16-18 and 21 June. Seismicity was at a very low level throughout, with occasional low-amplitude volcanic earthquakes."

"Activity remained at the generally low level that has persisted for several months. Occasional grey or brown ash emissions from Crater 2 were reported. Seismicity was at a very low level throughout, with only occasional small volcanic earthquakes."

"For the period September to November, activity remained at a low level. Occasional grey or brown ash emissions from Crater 2 were reported. Seismicity was at a very low level with only a few volcanic earthquakes recorded."

"Activity intensified in February after being at a very low level for about 1 year. Several large Vulcanian explosions at Crater 2 in late January marked the commencement of this new eruptive phase. Explosions occurred at rates of up to about 20 per day in February. The largest explosions produced eruption columns reportedly about 3-4 km high. No significant ashfalls took place in inhabited areas. Weak glow was frequently observed from Crater 2 up to about mid-February, and ballistic incandescent lava fragments were seen at the bases of some eruption columns. Seismicity accompanying this activity not only included the usual discrete explosion earthquakes, but also a number of periods of harmonic tremor, thought to be caused by sequences of prolonged gas discharge at Crater 2. Crater 3 remains inactive, except for mild fumarolic activity from the crater walls."

"Langila returned to a low level of activity in early March after a period of moderate-to-strong explosive activity at Crater 2 in February. From 3 March, activity at Crater 2 usually consisted of weak emission of white vapour, although occasional Vulcanian explosions took place. Crater 3 remained quiet."

"A new phase of increased activity at crater 2 began about 8 June. This followed several months of very weak activity punctuated by occasional mild Vulcanian explosions. From mid to late May a more prolonged period of slightly intensified activity consisted of grey ash emissions, occasional explosion sounds, and several periods of crater incandescence.

"Rumbling and explosion sounds, large quantities of blue vapor, and occasional grey ash clouds were reported from crater 2 between 8-12 June, marking the onset of a new phase of activity. A further intensification took place mid-month and an eruption column about 1 km high was reported on the 17th. Weak glow from crater 2 was observed on the night of the 20th, and explosion sounds were more frequently heard on the 22nd. Light ashfall was reported 10 km downwind on the 27th. Seismicity was comprised of characteristic Vulcanian explosion earthquakes. This higher level of activity was continuing at the end of June."

"Further intensification of the eruption at Crater 2 took place in July. Increased activity was noticeable from 19 July when the frequency of Vulcanian explosions increased from about 2 to 10 per day. These explosions were stronger, as indicated by ashfalls as far as 10 km downwind, louder detonations, and rumbling. Incandescent lava fragments were ejected on the night of 19 July. A further increase in activity was apparent from 22 July when daily totals of Vulcanian explosions climbed to about 30 and periods of continuous harmonic tremor were recorded."

"The stronger eruptive activity reported in late July declined rapidly at the beginning of August, but this was followed by two more spasms of intensified activity. More frequent Vulcanian explosions from Crater 2, accompanied by characteristic volcanic earthquakes and sequences of continuous harmonic tremor, took place 10-14 and 19-23 August. Weak red incandescence at the crater was observed from locations about 10 km downwind on 10 and 11 August."

"Activity intensified in September. A moderate phase of eruption began on 6 September when an ashfall was noted at Kilenge Mission (10 km NW of Langila). From 9 to 13 September, incandescence was noted at Crater 2 and there was an increase in audible explosions and rumblings (heard at the observation post, 10 km NW). Small incandescent ejections were reported on the night of 9 September. Seismic tremor lasting from a few minutes to a few hours was recorded during this period, with the strongest bursts on the 9th and 10th.

"Incandescence from Crater 2 was again noted 17-26 September with an increase of audible explosions and rumblings. During this period there were several ashfalls at the observation post and Kilenge Mission. Ash was also reported at Siassi, Umboi Island (30 km W) on 24 and 25 September. The brightest glow and highest level of tremor during this period were on 23 and 24 September."

"The eruption of Crater 2 persisted through October with periods of increased activity from 4-7 and 14-25 October. When inspected on 2 and 3 October, the 200-m-wide crater was only 50 m deep, plugged with a magma column covered by debris. High-pressure degassing was occurring from six fissures in the crater floor. Occasional explosions that may have been phreatomagmatic produced ash-laden plumes.

"Intensification of magmatic activity on the 4th resulted in sub-continuous Strombolian ejections to 250 m above the crater and intermittent Vulcanian explosions. A light to dark grey ash-laden plume rose 1500 m above the crater, and produced ashfall 10 km downwind. Loud rumbling noises and sharp explosions were heard at an observation post 9 km N of the volcano. Periods of seismic tremor lasting from a few minutes to a few hours were recorded during this time.

"Activity returned to the former degassing mode 7-18 October, but eruptions resumed after the 19th. The strongest seismic activity was recorded on the 19th and 20th but harmonic tremor lasted until the 24th. Strombolian eruptions were discontinuous 19-24 October and a few Vulcanian explosions expelled dark ash-laden columns to 2000 m above the crater. By the end of the month, the eruptive activity had declined to persistent degassing, with a few explosion shocks recorded daily."

"Activity was at a low level during November with occasional reports of grey ash clouds from Crater 2. A column of dark cloud was reported rising to about 200-300 m above the summit on the 30th. Two audible explosions (heard at the observation post, 10 km NW of the crater) were reported on the 17th and 30th. Crater 3 remained inactive throughout the month. Seismic activity remained at a low level throughout the month with only 2 explosion shocks recorded, on the 17th and the 30th."

"Activity was at a low level for most of December. Starting the 29th there were daily reports of rumbling sounds and light ashfalls at the observation post 10 km NW of the summit. Glow was noted from Crater 2 on the night of the 29th. Seismic activity also increased from the 29th, with several Vulcanian explosions recorded per day and some harmonic tremor.

"Moderate activity, which had begun in late December 1985 (10:12), continued for the first half of January. Numerous explosions from Crater 2 were seen, and there were daily reports of rumbling sounds at the observation post [9] km N of the summit. A light ashfall was reported at the observation post on 3 January. Occasional incandescence from Crater 2 was seen at night until the 13th. Low-frequency harmonic tremor was recorded on the 2nd, 3rd, and 7th. Numerous explosions (3-30/day) were recorded throughout January.

"A moderate level of activity continued in February. Crater 2 occasionally released white to greyish vapour. A number of explosion shocks (0-10 daily) were recorded, some of which were heard at the Cape Gloucester observation post . . . . Two periods of high background seismicity, consisting of sub-continuous, high-frequency 'tremor,' occurred 6-11 and 21-25 February, possibly related to periods of high rainfall. Weak, fluctuating glow was observed on the night of the 20th."

"Activity at Crater 2 in March was slightly higher than in February. Moderate to strong white to grey emissions were released intermittently throughout the month. Light ashfalls were reported [9] km downwind on 4 and 14 March. Weak night glows (with intermittent incandescent ejections) were reported on 16, 24, and 23 March. Explosion and rumbling noises were heard on the 4th, 9th, 14-16th, 18th, and 24-30th. Seismicity was at a moderate level with 2-10 Vulcanian explosion events/day."

"A further increase in activity at Crater 2 occurred in April. Weak to strong emissions of white to grey plumes were observed on most days and fine ashfalls occurred [9] km downwind on 2 and 27 April. Weak to moderate explosions and rumblings were heard on most days. Weak red crater glow was seen on ~30% of the nights and ejections of incandescent lava fragments were occasionally observed. Vulcanian explosions were recorded at rates of 0-3/day, but other higher frequency events and periods of harmonic tremor were also recorded."

"Crater 2 remained moderately active in May. White to grey emissions were reported daily with light ashfalls at the Cape Gloucester airstrip . . . on 11 days. Weak rumbling noises were reported on most days with occasional explosion sounds.

"Incandescence at the summit was reported 5-8 and 11 May. The brightest glow was on the night of 7 May. During this period of increased activity, explosion sounds were heard more frequently and 10-15 explosion shocks/day were recorded on the seismograph.

"During the last 5 days of May, activity decreased; emissions were weaker and no audible noises were produced by the volcano. There was no low-frequency tremor recorded during the month."

"Activity in June remained at the low level established in late May. Explosion sounds were heard on only two days (11th and 20th) and no sightings of crater incandescence were made. Emissions from Crater 2 were usually white vapours at low rates, but grey or brown ash emissions were noted on 11 days in the month. Fine ashfalls took place at the Cape Gloucester airstrip . . . on two days. Seismicity was at a very low level with only a few volcanic earthquakes recorded during the month."

"Langila remained at non-eruptive levels of activity with emissions restricted to weak white vapour. There were no reports of incandescence or audible sounds from the summits, and seismicity was at a very low level."

Weak to moderate amounts of white vapor issued from Crater 2 during December, but no sounds or summit incandescence were reported. Small quantities of ash fell at the observation post . . . on 15 December. A pilot described a black plume rising to 1,500 m on 3 January but the report could not be confirmed by the local observer. Seismic activity remained at a low level.

Activity remained at a low level in January. Weak to moderate white to occasionally grey [emissions] from Crater 2 were observed. There were no reports of audible sounds or incandescence from the summit. Seismic activity remained at a low level.

Activity continued at a low level during March. Crater 2 emitted mostly weak white vapour with occasional ash clouds. There were no reports of sound effects or incandescence from the summit. Seismicity remained at a low level.

Activity was generally at a low level in April with weak white vapour emission from Crater 2 and little or no activity at Crater 3. However, a strong explosion occurred at Crater 2 on 12 April, propelling an ash cloud to ~3 km above the volcano. The explosion was heard [9] km away where fine ashfall was noted. Preliminary examination of the ash indicated that it contained little or no fresh material.

Activity . . . continued at a low level in October except for a single explosion on the 9th, which produced a dark brown ash column ~300 m high. Weak-moderate white vapour was emitted continually from Crater 2 during the month, while Crater 3 was quiet.

A moderate increase in activity began the second week of November; a weak glow from Crater 2 was noted, accompanied by low rumbling noises and a weak-moderate white-gray plume. Seismicity showed no significant change and there was no activity from Crater 3.

Activity continued at a low level in December. Weak to moderate, pale grey emissions from Crater 2 were noted occasionally throughout the month, and weak rumbling, roaring, and explosion noises were heard on a few days during the first half of December. Weak glow from this crater was seen on two days at mid-month.

Low-level emissions and seismicity continued during January. Crater 2 emitted small amounts of white vapor for most of the month. Weak glow from Crater 2 was observed at night 17-22 January. For several hours on the morning of 23 January it produced a dark gray ash column.

Low-level activity continued during February. Emissions consisted of weak white vapors from Crater 2 for most of the month. Weak explosion sounds were heard on 8 and 21 February, then more frequently between the 25th and 27th. Weak, deep, roaring noises were heard starting on the 13th and a weak night glow was observed 27-28 February. Crater 3 was inactive. Microseismicity remained at a very low, non-eruptive level.

Eruptive activity was at a low level throughout March. Background activity consisted of release of small volumes of white vapour from Crater 2, with occasional deep, low rumbling noises. Weak to loud explosion sounds were heard at 1- to 8-day intervals. The largest explosions (on 4, 11, 12, 14, and 17 March) ejected ash-laden clouds to 300-600 m above the crater, causing light ashfalls on coastal villages. The main explosions (Vulcanian or phreatomagmatic) were followed by a period of incandescent, Strombolian-like projections to ~60 m above the crater rim and a bright to dull crater glow that persisted for a few hours. Crater 3 was inactive except for weak greyish vapour emission 2-4 March. Microseismicity remained at a low level, although the major explosions were recorded.

"Activity continued at a low level throughout the month. Crater 2 occasionally emitted weak to moderate white vapours. Occasional deep, low, rumbling noises were heard throughout the month, and one deep explosion on 3 April was accompanied by a weak ejection of incandescent lava fragments. Crater 3 continued to be relatively inactive, with only weak vapour emissions on 16, 28, and 29 April. Seismicity remained at a low level with occasional Vulcanian explosion events recorded."

"Activity remained at a low level during May. Crater 2 occasionally produced weak to moderate white-grey emissions. Low rumbling noises were heard on the 19th, 20th, and 24th-26th. Weak glows from this crater were seen on 4, 18, 19, and 22 May. Crater 3 remained virtually inactive, with only weak white vapour emissions on the 21st and 24th. Seismicity remained at a low level with occasional Vulcanian explosion events recorded."

"A generally low level of activity continued during the first half of July. Crater 2 produced occasional weak emissions of pale-grey ash and vapour, sometimes accompanied by weak explosions. From about 19 July, more sustained explosive activity occurred. Light ashfalls were reported ~10 km from the crater on 20 and 21 July. Weak red glow from the crater was seen on the night of the 21st. Only a few explosions were large enough to be recorded at the seismic station . . . ."

"Crater 2 continued to release white with occasional grey [emissions] at low rates. Deep low rumbling sounds were heard on 1, 6, 13, and 24 August and weak red glow was observed on the 5th, 18th, and 22nd."

"Low-level activity continued in September. Weak-moderate white emissions and occasional grey ash clouds were released from Crater 2. Explosion and rumbling sounds were heard on a number of days and weak crater glow was observed on the nights of the 5th and 14th. No eruptive activity took place at Crater 3. Seismic activity was low and only a few explosion earthquakes were recorded during the month."

"Activity increased slightly in October. Weak to moderate white with occasional grey emission continued from Crater 2 throughout the month. Steady weak glow was observed for about a week (5-11 October) at Crater 2. Two loud Vulcanian explosions occurred on the 27th and 30th. Crater 3 remained relatively inactive with only weak white and grey emissions on 1, 5, 8, 9, and 17 October."

"Activity returned to a low level in November. Weak-moderate amounts of white vapour with occasional grey [ash] were emitted from Crater 2. Weak rumbling noises occasionally were heard on the 4th. Ashfall was observed on the 11th. Two Vulcanian explosions, on the 18th and 27th, were accompanied by ash columns that rose a few hundred meters. Crater 3 was inactive throughout the month. Seismicity remained low and only 9 explosion earthquakes were recorded."

"Low-level activity continued in December. Weak to moderate white emissions with occasional grey ash clouds were released from Crater 2. Weak rumbling noises were heard 28-31 December. A Vulcanian explosion on the 4th ejected an ash column that rose a few hundred metres and resulted in light ashfall to the SE. Crater 3 remained inactive throughout the month. Seismic activity remained at a low level with <10 events/day near the end of the month."

"Activity increased slightly on 26 December and continued into January. A number of low-frequency explosion earthquakes (2-9) were recorded daily, some of which were accompanied by loud detonations heard at the the observation post . . . . Weak to loud rumbling noises were often heard and moderate pale-grey ash and vapour clouds were released from Crater 2. Weak red glow was observed at the summit on the nights of 4 and 9-11 January, by which time the number of explosion shocks had decreased to 1-3/day. One louder Vulcanian explosion took place on the 11th, producing a thick dark ash column. Weak red glow was observed again on the nights of 15-16 January and occasional weak rumbling noises were heard until the 21st. Occasional weak vapour emissions were observed from Crater 3 on the 4-5th, 10-11th, 13th, and 22nd."

"Activity declined somewhat in February following the slight increase in late December-mid January. Weak-moderate emissions of white to pale-grey vapour and ash clouds were released from Crater 2 during most days of the month. Occasional weak rumbling noises were heard from Crater 2, and detonations were heard on the 14th and 22nd. Weak red glow from this crater was seen 6, 8, 9, 23, and 24 January. Crater 3 remained inactive throughout the month."

"There was a slight increase in March in the overall low level of inter-eruptive activity since the last significant eruption in March-May 1986 (SEAN 11:3-5). During the first week of March, 2-7 low-frequency explosion earthquakes were recorded daily, some of which were accompanied by detonations heard at the observation post . . . . Weak rumbling noises were occasionally heard and weak red glow was reported on the nights of 28 and 29 March. Vapour emission from Crater 2 was of moderate volume throughout the month with occasional grey ash clouds. Crater 3 was inactive."

"The slightly stronger activity from Crater 2 reported in March continued in April, although fluctuations in the level of activity were evident. The volcano was quiet at the beginning of the month. Between 5 and 23 April, moderate ash emissions were observed, accompanied by weak to strong rumbling sounds. Most ash fell near the volcano. On most nights during this period, weak red glow was observed above Crater 2. Activity subsided between 24 and 28 April, but on the 29th and 30th returned to the levels seen at mid-month. Seismic records were unavailable between 14 and 30 April. During the first half of the month, seismicity was at a low level with only 0-1 explosion earthquakes/day."

"The slightly stronger activity . . . continued through May. Moderate grey emissions were released from Crater 2 throughout the month, accompanied by occasional weak rumbling noises. One loud explosion was heard on the 30th. Weak red glows from this crater were seen 23, 29, and 30 May, and incandescent lava fragments were ejected above the summit on the 30th. Occasional, thin, white-grey emissions were observed from Crater 3 on 1-4, 7-8, 16, 19-20, 24, and 29-31 May, more frequently than normal."

"Langila returned to very subdued activity in June. Crater 2 released moderate white-grey emissions, accompanied by occasional rumbling noises. Explosions were heard on 1, 2, 6, 24, and 30 June, and a weak red glow was seen above this crater on the night of the 14th.

"When the volcano was inspected on 10 June, Crater 2 had enlarged and deepened since the last field inspection in October 1985 (10:10). The flat, [40]-m-wide, annular platform that formerly surrounded the crater had caved in, resulting in an estimated [130]-m wide crater with a narrow ledge. The crater now has a composite funnel shape produced by the sinking of the former magma plug in two successive steps. The top of the active plug (responsible for the occasional night glow) is now at ~1,045 m altitude (the crater rim is at 1,100-1,120 m) and clogged by debris from sub-continuous rocksliding.

"Crater 3 . . . remains inactive. The crater is sealed at ~900 m asl by a flat muddy floor from wash-outs of the walls (the crater rim is at 1,045-1,080 m altitude). The source of white vapour occasionally observed from the observatory is an active fumarole at the base of the sub-vertical S wall."

"A steady decrease in volcanic activity was observed at Crater 2 during July, while Crater 3 remained inactive. Emissions from Crater 2 were mostly white but occasionally grey (on 7, 16, 18, 20, 21, 26, and 27 July), and weak to moderate in volume. Occasional low rumbling sounds were heard from the 1st to the 20th and on the 28th. One loud explosion on the 16th accompanied the ejection of thick brownish-grey ash, forming a column that rose 1200 m above the crater. Night glow around the crater mouth was visible only on the 1st and 5th."

"Activity intensified somewhat during September. Weak explosive activity took place at Crater 2 on most days. The ash content of emissions was generally low, but ashfalls were recorded [~9] km downwind on the 5th and 16th. Sound effects at the observation post usually consisted of weak rumblings, but one loud explosion was heard on the 16th."

"After 2 months of very weak activity, night glow was seen over Crater 2 on the nights of 7, 17, and 20 October, and steadily from the 24th to the 26th. Weak glow on the night of 30 October was followed on the 31st by a Vulcanian explosion that resulted in light ashfall on the coast, 10 km downwind. The amount of vapour released by this crater increased throughout September and October. Low rumbling noises and occasional discrete explosion sounds were heard. There was no sign of activity from Crater 3 . . . , apart from occasional wisps of white to greyish vapour. Seismicity increased at the beginning of the month from a background of a few tens to several hundreds of moderate-amplitude B-type events/day, occasionally merging into periods of sub-continuous tremor lasting several minutes."

"Activity remained at a moderate level in November. Vapour was released by Crater 2 in small to moderate amounts. Deep rumbling noises and a weak red glow were reported at the beginning (1st and 2nd) and end (29th and 30th) of the month. Crater 3 released weak [emissions of white vapour]."

"Although a weak red glow was observed over Crater 2 on most nights of the month, activity at Langila remained at a moderate level throughout December. Vapours were emitted in small to moderate amounts, and deep rumbling noises were occasionally heard. The seismicity consisted of a few tens to several hundreds of small-amplitude B-type events/day."

"Activity remained at a moderate level throughout January. Weak red glow was observed over Crater 2 on every clear night of the month. Vapour was released in weak to moderate amounts. The seismicity consisted of numerous daily B-type events of small amplitude and an occasional Vulcanian explosion shock. Crater 3 was inactive except for weak fumarolic emissions."

"Moderate vapour and ash emissions continued at Crater 2. Ashfalls were mainly in uninhabited areas SE of the volcano, but on one occasion there was a fine ashfall ~10 km to the NW. Weak red crater glow was often seen at night. Seismicity was generally at a low level. Vulcanian explosion earthquakes were occasionally recorded."

"Activity consisted of weak to moderate white-grey emissions from Crater 2. Weak, steady, red glow was observed 1-4 and 25-31 March. Rumbling noises were heard on the 28th and 29th. Crater 3 remained quiet throughout the month. Seismicity was at a low level."

"Activity was limited to weak or moderate emissions of white vapour from Crater 2, with a weak, steady, red glow at night from 25 March until 6 April, and 9-11 and 27-28 April. Occasional weak, deep rumbling noises were heard on 3 consecutive days 12-14 April. Crater 3 remained inactive, apart from thin white vapour released by fumaroles in the crater."

"A low level of activity prevailed at Langila. Crater 2 released white vapour in moderate amount during the first half of the month, when a steady night glow could be seen (until the 17th). From the 20th onward, 1-3 explosion earthquakes were recorded daily while background seismicity remained at a low level. The amount of vapour released by Crater 2 decreased in the last week of May. Crater 3 remained inactive, apart from thin white vapour released by fumaroles in the crater."

"A low level of activity prevailed . . . although there was an increase toward the end of the month. Crater 2 released a weak to moderate vapour and ash cloud while Crater 3 remained virtually inactive. Vulcanian explosion earthquakes were recorded occasionally. A weak red glow was observed over Crater 2 on most nights after 23 June."

"An increase in activity at Crater 3, which had been inactive since April 1983, began towards the end of June and continued during July. The increased activity was characterized by emission of white, grey, and brown vapour and ash clouds with occasional blue vapour. Explosion earthquakes were recorded on most days with daily totals ranging from 0 to 14 events. They were often accompanied by tremor lasting 1-10 minutes and the rise of Vulcanian ash clouds over the crater. Ashfalls were reported in areas N and NW of the volcano. Occasional deep rumbling noises were heard after the 8th. A weak glow was seen on 16-18, 24, and 31 July.

"Crater 2 released white, grey and occasional blue emissions. Steady night glow was seen throughout the month without any other sign of eruptive activity."

"Moderate Vulcanian activity involving Crater 3 continued. Crater 3 . . . was releasing a plume of white vapour with frequent ash-laden clouds accompanied by weak Vulcanian explosions. The largest of these explosions (recorded by the nearby seismometer) totaled as many as 35/day. Ashfalls were reported in areas N and NW of the volcano. Rumbling noises were heard on 7 August and glows were observed on the 13th and 18th, associated with weak explosions.

"Moderate Vulcanian activity involving Crater 3 continued in September. Crater 3 produced frequent mild Vulcanian explosions, with occasional larger ones (6-38/day). The larger explosions, which ejected clouds to as much as 500 m above the crater, generated large-amplitude, impulsive seismic signals, while many of the smaller explosions were almost aseismic. A small pyroclastic avalanche may have been produced on 2 September. Incandescent rocks were observed tumbling down the NW flank at about 0330, accompanied by loud explosions and rumbling sounds. Ashfalls were reported from inhabited areas ([~9] km downwind) on six days. Ejections of incandescent lava fragments were reported 3-5 September, and steady crater glow was observed on 10 September.

"Activity at Crater 2 consisted mainly of weak-moderate emissions of white vapour, with rare ash emissions. The emissions sustained a column 100-200 m high and a plume several kilometers long. Deep rumbling sounds were heard on many days, and weak crater glow was frequently observed.

"An aerial inspection on 3 September revealed that Crater 3 is ~100 m in diameter and its N rim is markedly lower than the S rim. The active vent is in the N part of the crater and has built a small cone of ejecta. Crater 2 is ~150 m across and has a shallow bowl shape. The active vent has formed a funnel-shaped crater in the NE part of Crater 2."

"Activity returned to a low level in October . . . . Emissions from Crater 3 consisted mainly of occasional weak to moderate, white and grey, ash and vapour clouds. Deep, low, explosion and rumbling noises were heard on 6 and 7 October, respectively. Weak steady glow was observed on the 6th and the 9th. Activity at Crater 3 was somewhat subdued during the last week of October. Crater 2 released weak and occasionally moderate white and at times blue vapour throughout the month. Deep weak rumbling noises were heard between 16 and 28 October and steady weak glow was seen throughout the month."

"Activity remained at a low level in November . . . . Crater 3 emitted mainly weak to moderate white-grey ash and vapour clouds. However, stronger emissions on 12 and 25 November produced eruption columns ~200 m high and ashfalls ~10 km downwind. Weak deep explosions from Crater 3 were heard on 28 and 29 November. Emissions from Crater 2 consisted mainly of weak to moderate white and grey vapour and ash, and rarely, blue vapour. Steady weak glow was observed throughout the month. The only sound from this crater during November was a deep loud explosion on 28 November and rumbling noises on the 29th and 30th. Seismic activity was at a moderate level."

"Activity was at a moderate-low level in December. Crater 2 occasionally emitted weak-to-moderate white and grey vapour and ash clouds. Weak rumbling from Crater 2 was heard 12 December. Steady weak red glow from this crater was observed at night on 7, 8, 12-17, 28, and 31 December. Activity at Crater 3 was similar to that at Crater 2. Night glow from the crater was seen once, on 7 December.

"Seismic activity was at a moderate level during the first half of the month (up to ~30 explosion earthquakes/day), but declined to a low level at mid-month. During the second half of the month, daily totals of volcanic earthquakes were in the range 0-4."

"Activity was steady at a low level throughout January, as it has been since mid-October 1990, and was essentially limited to Crater 2. Even though that crater maintained a weak red glow at night, emissions were limited to small volumes of white-greyish vapour and ash. Emissions from Crater 3 were very weak. Only one explosion earthquake was recorded during 11 days of seismic monitoring."

"Activity remained at a low level in February. Crater 2 continued to produce weak-moderate emissions of white to pale grey vapour and ash, and at night a steady weak red glow was observed over the crater. Crater 3 emissions consisted of white vapour released at very low rates. Seismicity was also at a low level. On most days there were no volcanic earthquakes, but between 6 and 16 February up to 4 events/day were recorded."

"A slight increase in activity was evident towards the end of March. Explosions from Crater 2 were more common from the 24th, producing grey ash and blue vapour emissions. Light ashfalls were observed on the NW slopes of the volcano. Steady weak red glow from this crater was observed most nights. Seismicity was very weak for most of March, but from the 24th onwards, 2-8 explosion events/day were recorded."

"Activity declined in early April . . . . Emissions from Crater 2 consisted of moderate to weak white-grey ash and vapour. An explosion on 3 April produced a dark ash column that rose ~500 m above the crater and resulted in ashfall on the NW side of the volcano. Steady weak red glow from the crater was observed on most nights. Following the first few days of stronger seismicity, when up to four explosion earthquakes/day were recorded, the seismicity declined and on most days no explosion events were recorded."

"After 7 months of quiescence, Crater 3 was reactivated. Resumption of activity, which started on 16 May, was manifested by the release of moderately thick white-to-grey vapour clouds with occasional blue vapours, and the recording of explosion earthquakes (2-20/day). After 18 May, deep rumbling noises and/or loud Vulcanian explosions were heard at the Cape Gloucester observation post . . . and light ashfalls occurred on the NW flank of the volcano. A weak steady red glow was observed over this crater at the end of the month.

"Activity at Crater 2 . . . did not seem to be affected. This crater kept on releasing moderate to weak emissions of white vapour and displayed a steady weak night glow."

"Crater 3 . . . produced 1 to >40 Vulcanian explosions/day in June. The explosions produced dark grey vapour and ash clouds or columns, resulting in light ashfalls over the NW flank of the volcano and to coastal villages (10-15 km distant). Villagers were also shaken by the airwaves of the strongest explosions. Night activity consisted of weak red glow, with the largest explosions producing a short-term brighter glow between 5 and 16 June.

"Crater 2 released weak to moderate white vapour emissions plus occasional grey ash and blue vapours. The crater produced one loud Vulcanian explosion on 28 June, accompanied by an ashfall. A steady weak night glow was visible over the crater for much the same period as at Crater 3 (3-17 June). After a 10-day absence, night glow reappeared at Crater 2 on 28 June, following its throat-clearing Vulcanian explosion. Two days later, night glow also returned to Crater 3.

"The daily number of Vulcanian explosions from Crater 3 reached its maximum level of >30 between the 15th and 19th, coinciding with the absence of night glow at both craters (figure 3). A seismograph 9 km away (CGA), which previously recorded ~10% of the explosion earthquakes detected by the summit station (LAN), started to record an increasing proportion of these events (to >50%)."

Figure 3. Number of explosion earthquakes/day recorded at Langila's summit seismic station (LAN) and a second station (CGA) 9 km away, late May-early July 1991. Periods of glow at craters 2 and 3 are shown by shaded areas along the bars at bottom. Courtesy of RVO.

"Activity of both craters remained moderately strong in July, as in June. Crater 3, which had resumed activity in mid-May, released white-to-grey vapor and ash clouds, and light ashfall occurred towards the NE of the volcano on the 6th and 8th. Occasional weak to loud explosions were heard throughout the month. Weak to bright red glow was observed on the 8th, 9th, 13th, and throughout the last week of the month.

"Activity at Crater 2 was characterized by the emission of moderate to thick pale grey ash clouds. Occasional loud to low explosions, some of which were accompanied by light ashfall, were heard during the second and last week of the month. Steady, weak night glow was visible throughout the second week and on the 22nd and 23rd.

"Seismicity remained high throughout the month, with the occurrence of explosion earthquakes and tremor. The daily number of Vulcanian explosions recorded by the summit station (LAN) reached a maximum of 40-60 between the 21st and 26th. Tremor, hardly noticeable in May, occurred almost daily in June-July (up to 100-200 minutes/day). Two types were recognized: high-frequency, discontinuous tremor periods, lasting 1-2 minutes; and lower-frequency harmonic tremor, continuous for periods of several (up to 10) minutes. The tremor became strong enough to be recorded at both the summit station (LAN) and the 9-km-distant CGA station."

"In August, Crater 3 frequently erupted moderate to strong, pale grey-brown ash and vapour clouds accompanied by weak to loud detonations, roaring or rumbling. The eruptions occurred at intervals of several minutes to a few hours. The emission clouds rose as much as 500 m above the crater. Dull to bright red crater glow was observed on the nights of 7-9, 12, and 13 August.

"During an aerial inspection on the 14th, two active vents were observed in a mound of lava filling Crater 3. The vents were ~5-10 m in diameter, 40 m apart and aligned approximately N-S. The N vent was more active and was filled with incandescent lava. The S vent was clogged with dark lava. Both vents released blue vapour. Lava had flowed eastward to form a short (70 m) lobe in the E part of the crater. A longer (~150 m) lobe of lava was present on the NE flank of Cone 3. This lobe was fresh, having a dark surface, and its source appeared to be a tube within the E lobe. The NE-flank flow was first observed on 13 August, and appeared to be inactive then. However, some activity of this flow had been evident the previous night when prolonged incandescence in this area and some movement of incandescent material were observed. Two other very small lava lobes (both inactive) were observed on the NW flank of Cone 3.

"Throughout the month, Crater 2 (roughly 200 m E of Crater 3) almost continuously emitted moderate amounts of pale grey-brown ash and vapour. This activity was accompanied by nearly continuous low roaring sounds. Occasional stronger explosions took place. Dull glow over the crater was observed on the nights of 7-9, 13, 22, 24, and 27 August. A 30-minute period of strong explosive activity on the night of 13 August resulted in a large volume of incandescent lava fragments being ejected onto the NE flank of Cone 2. Incandescent lava-fragment ejections from Crater 2 were also seen on the night of 20 August. A brief aerial view of the interior of Crater 2 on 14 August indicated that it remains funnel-shaped, with several benches. Detailed observation was prevented, however, by emissions of ash and vapour.

"The ash plume from the combined emissions of the craters was usually directed in a sector between NNE and NW. Fine ashfalls were recorded in coastal areas (9 km distant) on 1, 2, 6, and 12 August.

"Seismicity remained at a moderate to high level throughout the month. It appeared that most of the stronger seismicity was associated with events at Crater 3. The daily number of explosion earthquakes recorded by the summit station fluctuated between 20 and 70, with the largest totals of 40-70 events on 16, 25, and 30-31 August. Meanwhile, the remote station (9 km distant) recorded 0-29 events/day. Numerous low-amplitude, short-duration, tremor-like signals were produced by weaker explosions. Several periods of harmonic tremor were recorded but the source was not determined."

"Moderate to strong activity persisted at Langila throughout September. Ash-laden vapor emissions were released almost continuously from Crater 2, accompanied by weak to loud rumbling sounds. A weak glow was visible on most nights, except 21-25 September. Activity at Crater 3 consisted of occasional Vulcanian explosions, at rates of 30-80/day. The activity was stronger 23-26 September and a steady night glow was visible 25-26 September.

"The amplitude of discontinuous tremor declined markedly in late August, while cumulative daily tremor duration dropped to <=100 minutes from levels that had been as high as 200 minutes/day since mid-June."

"Moderate to strong activity persisted throughout October. Crater 2 activity consisted of continuous release of white vapour, producing a small emission column that frequently (5-15 times/hour) turned into a forceful jet of ash-laden vapour, generating a whooshing sound. Occasionally, a discontinuous tremor-like signal was recorded by the 1-km-distant LAN seismometer. Light ashfalls were experienced in coastal areas 10 km downwind. On most nights this Vulcanian activity was accompanied by dull glow above the crater, becoming brighter at times when incandescent lava fragments were ejected onto the flanks of the cone.

"Activity at Crater 3 was intermittent, with periods of 5-15 minutes devoid of any emission separated by sudden forceful explosive emissions of thick, mushrooming, dark grey ash clouds that rose 400-650 m above the crater rim. The crater was more strongly active 4-10 October, when small pyroclastic flows were generated at the base of the strongest explosions, but these did not advance beyond the cone's upper flanks. Intermittent glow from the crater was accompanied by incandescent projections to ~100 m above the crater rim. Crater 3 explosions were recorded as distinct impulsive signals (5-50/day) by the LAN seismic station, with the strongest ones (1-12/day) recorded 9 km away (CGA station).

"Seismic activity dropped significantly in October. The intermittent tremor recorded since June disappeared in September but reappeared sporadically in October. Most of the seismicity consisted of discrete earthquakes. The daily totals of these events ranged from 15 to 60.

"Aerial and ground inspections were carried out 10-11 October. The main change noted since the last inspection, in mid-August, concerned Crater 3. Of the 2 active vents previously observed in the mound of lava filling the original crater, the N one (which seemed the most active in August) was inactive, while a 50-m explosion crater had formed around the S vent, which was the source of the reported Vulcanian activity. This new crater was bowl-shaped, ~6 m deep, and filled with loose debris-blocks and ash. Similar debris also extended in short tongues to <100 m outside the crater rim and probably was deposited by small pyroclastic flows such as those reported earlier in October. Within the crater were irregular arcuate ridges of loose debris that may have been deposited by pyroclastic flows. The active vent area was only ~5 m across. Although it remained glowing for a short time after each explosion, the maximum temperature measured with an infrared thermometer from 30 m distance was only 500°C when erupting, and 270°C when quiet. The temperature of the crater floor was 140-170°C.

"The short lava flow observed 12 August on the cone's N flank had cooled, but a few rootless fumaroles remained on its surface, which was partly buried under airfall blocks and ash. The flow had the rugged surface features of aa lava and was ~300 m long, extending from the crater rim (~1,100 m elev) to 950 m elev. Its thickness decreased from 2.5 m (where it spilled over the crater rim) to <1 m at its front. The volume of the flow is estimated to be <=15,000 m3.

"Crater 2 was estimated to be 130 m wide and 30 m deep. Its floor is now at the level of the upper bench described in the last ground inspection, in June 1989 (SEAN 14:06). Several small vents (<=1 m in diameter), although closely grouped at the base of the crater, were activated independently. At the times of the strongest emissions however, up to four vents erupted concurrently with a deafening jet engine noise, generating air and ground vibrations recorded by the summit seismic station as emergent periods of tremor-like signals. The westernmost vent was directing its jet of ash-laden vapour at an angle of 15° toward the SE, resulting in the backfall of blocks and spatter-like scoriae on the SE crater rim and beyond. The maximum measured temperature at the base of the jet (although glowing at times) was only 240°C, and 70°C higher up in the plume."

"Activity at Crater 2 remained moderately strong, while a slight decline was evident at Crater 3. Crater 2 activity consisted of continuous emission of pale ash clouds accompanied by occasional low rumbling noises. From 17 November onward, activity increased with occasional forceful eruptions of grey ash clouds, rising several kilometres above the crater, accompanied by loud or deep rumbling and explosion noises. Light ashfalls were recorded on 17, 25, and 28 November in coastal areas 10 km downwind . . . . Steady weak night glow was visible over the crater during the first half of the month, and ejections of glowing lava fragments to ~100 m above the crater rim were observed 17-26 November.

"There was a further drop in Langila's seismic activity in November as a result of the decline in Crater 3 activity. The summit seismometer continued to record discontinuous tremor-like signals until 23 November. The daily totals of discrete events ranged from 1 to 28."

"Activity was at a moderate-low level in January. Crater 2 emitted white to grey ash and vapour clouds at moderate to low rates. However, on 21 January, dark ash-laden clouds rose several hundred meters above the crater rim and resulted in light ashfalls on the SE side of the volcano. Deep loud or low rumbling and explosion noises accompanying the emissions were heard throughout the month. Steady, weak red glow from this crater was observed at night on 9, 19, 24, 27-28, and 31 January. Crater 3 activity consisted mostly of emissions of weak white vapour. No noises were heard, although weak night glow was seen on 9 and 28 January around the crater rim. Seismic activity was at a low level throughout the month. Daily totals of volcanic earthquakes (all at low frequency) ranged from 0 to 16 . . . ."

"During February the activity continued to be focused at Crater 2, at an intensity similar to that observed in January. However, seismicity increased in the second half of February. Emissions at Crater 2 consisted of pale-grey vapour and ash clouds in low-moderate volumes. Occasionally there were ashfalls on the lower flanks of the volcano. Explosions and rumbling sounds associated with the emissions were heard throughout the month. When the summit was free of cloud at night, a steady weak glow was seen above the crater. Activity at Crater 3 was mostly confined to weak emissions of white and blue vapours. However, there was a large explosion on 11 February that produced an emission cloud ~1 km high. Seismicity was steady at a low level in the first half of the month but then began to increase. By the end of the month seismicity had reached the level recorded in January (up to 17 low-frequency earthquakes per day)."

"Activity increased in March with Crater 3 becoming more active. Emissions from Crater 3 consisted of weak to moderate white-grey vapour and ash with occasional blue vapour. Weak to moderate explosion noises were frequently heard throughout the month. At night, weak to moderate red glow over the crater and occasional incandescent lava ejections were seen. A new lava flow on the cone's N flank began on 6 March and was still advancing at the end of the month. Emissions from Crater 2 consisted of low to moderate volumes of white-grey vapour and ash clouds. Thick black ash clouds were emitted towards the end of the month, resulting in ashfall on the SE side of the volcano. Rumbling and explosion noises associated with some of the emissions were heard throughout the month. Steady weak red crater glow was observed on clear nights, with incandescent lava ejections occurring on 21 and 22 March. Seismic activity was at a higher level than in January and February."

"Moderate eruptive activity continued during April. Crater 2 emitted moderate volumes of pale grey ash and vapour, and occasionally there were stronger explosions that propelled ash clouds several kilometers above the summit. Ashfalls to 10 km from the source were common. Explosions were heard at the observation post . . . on most days between 1 and 11 April. Rumbling and roaring sounds were heard on 27-30 April. Steady, weak crater glow was seen on most nights. Crater 3 activity was mild at the beginning of the month, and only weak white emissions were seen. Lava flows that began 6 March ceased on 1 April. Crater 3 became more active on 6 April; however, the ash content of emissions remained low. Incandescent lava ejections and/or glow were reported on most nights beginning 6 April. The ejections rose as much as 500 m above the crater. Beginning on 9 April, the explosive activity was stronger and emissions contained more ash. Explosion noises were reportedly loud at the observation post.

"In early April, seismicity appeared to mainly reflect the activity at Crater 2, while during 7-14 April, most of the seismicity was associated with Crater-3 activity. All seismic monitoring ceased on 19 April with the failure of both seismic stations."

"Moderate eruptive activity continued during May. Crater 3 was the most steadily active. Throughout the month it produced intermittent weak and loud explosions with forceful emission of grey ash columns rising to several hundred meters above the crater. No night glow was seen until 29 May. Activity at Crater 2 was moderately strong on 1 May, with forceful dark ash clouds rising several km above the crater. After the 1 May episode, activity was relatively mild. Other than moderate volumes of white and occasionally blue vapour emission, it only produced Vulcanian explosions on 11 and 18 May.

"Both craters were reactivated on the last few days of the month. Weak incandescent projections started at Crater 3 on the night of 29-30 May. On 30 May, low to loud explosions and whooshing noises accompanied bright Strombolian ejections to 700 m above the crater. Also on 30 May, a thick, dark ash column a few km high was emitted by Crater 2, with nighttime incandescent fragments rising 125 m above the crater. On 31 May, the activity was mainly from Crater 3, with ongoing high Strombolian projections, emission of a thick grey ash column several km high, and the production of a new, short lava flow down the NW flank of the cone. Unfortunately, failure of both seismic stations prevented recording of any related seismicity. The recurring activity from both craters continued into early June, producing much ashfall on the downwind coastal areas."

"A new phase of eruptive activity that started on 30 May lasted until 8 June. From 1 to 4 June, both Crater 2 and Crater 3 produced ash-rich Strombolian explosions to 500-700 m height. A new, short lava flow was emplaced on the NW flank of Crater 3. Emissions from Crater 2 became markedly ash-laden 4-7 June, with a plume rising a few kilometers above the crater and ashfalls on coastal areas 10 km NW. After the 7th, only weak to moderate vapour emissions and occasional Vulcanian explosions were noted from Crater 2.

"Activity at Crater 3 also waned after the first week in June, although more progressively. On the night of 7 June, intermittent explosions projected incandescent lava fragments to 250 m above the crater, while on 8 June there was weak steady glow over the crater. Intermittent explosions still occurred daily until the 24th, producing dark convoluting ash clouds that rose a few hundred meters above the crater.

"Seismic monitoring resumed on 11 June and showed only low-level activity throughout the rest of the month."

"Weak-to-moderate eruptive activity continued in July. Lava effusion at Crater 3 from 25 to 27 July or longer was associated with increased explosive activity late in the month.

"Activity at Crater 2 was at a low level 1-19 July with emissions of weak white vapour, occasionally blue or containing ash. A weak explosion probably associated with Crater 2 was heard on 1 July. There was no night glow during this period. Crater 2 was more active from 20 July until the end of the month. Loud-to-low rumbling noises and explosions were heard, accompanied by emissions of weak-to-moderate, occasionally thick, grey ash clouds. Weak night glow was observed from 20 July onward.

"Activity at Crater 3 was also low for most of the month, punctuated by occasional forceful emissions of grey-to-brown ash clouds, sometimes reaching more than 1 km above the summit. Activity increased to a moderate level from 25 July with audible explosive activity, night glow from the summit crater, and emission of a lava flow on the cone's N slope. The summit was obscured by clouds from 25 July and it was not clear whether the flow was still active. The explosion noises that started on 25 July continued until the end of the month. Light ashfalls ~10 km downwind from the volcano were noted on 5 and 22 July. Seismic activity was at a low level throughout the month despite the increase in visual activity."

"Moderate activity prevailed . . . throughout August. Activity at Crater 2 consisted of weak emissions of white and blue vapour with occasional rumbling sounds. From the 19th onward, the volume of gas and vapour emission increased, explosion sounds were heard intermittently, and a night glow was seen above the crater. Activity at Crater 3 was limited to occasional emission of white to grey vapour clouds. Seismicity remained low throughout the month, with only a few explosion shocks recorded daily."

"A moderate level of activity continued . . . in September. Activity at Crater 2 consisted of emission of white-to-grey vapour-and-ash clouds, occasionally with blue vapour. The emissions were accompanied by weak roaring noises. Weak night glow over the crater was seen 1-6 and 27 September. Emissions from Crater 3 were similar to those of Crater 2. Occasional weak explosions started on 6 September and continued until mid-September. No night glow was observed from the crater. Seismicity remained low throughout the month."

"Activity . . . was at a lower level during October than in previous months. Emissions from both craters consisted of weak-to-moderate white-to-grey vapour-and-ash clouds. Blue vapour was occasionally released from both craters during the latter part of the month. There was no glow observed throughout the month. Noises were heard from Crater 2 on the 31st. Seismicity remained low throughout the month."

"Activity at Langila's Crater 2 fluctuated in November. During periods of stronger activity, on 1-10, 15-17, and 23-26 November, moderate ash emissions occurred with eruption clouds rising several kilometres above the crater. This resulted in light ashfalls to at least 10 km downwind. At night, incandescent ejecta were visible in the eruption column. Detonations, roaring, and rumbling accompanied the activity. Between phases of stronger activity, white-grey, lightly ash-laden clouds were released less forcefully.

"For most of the month, Crater 3 released weak-to-moderate white-grey vapour-and-ash clouds. Blue vapour was also released. A brief phase of stronger activity took place 28-29 November when ash contents of the emissions were greater and eruption clouds rose several kilometres above the crater. There was an unconfirmed report of a new lava flow from Crater 3 on the 28th.

"Seismic activity appeared to reflect the visible fluctuating explosive activity at Crater 2. Up to 15 explosion earthquakes/day were recorded. During the brief phase of stronger Crater 3 activity, periods of harmonic tremor were recorded."

"Moderate eruptive activity continued at Langila during December. Emissions from Crater 2 throughout the month consisted of weak-to-moderate white vapour-and-ash clouds, accompanied by occasional forceful emission of thick dark-grey and brown ash plumes rising several kilometers above the summit. Fine ashfalls were reported on 4, 12, 19, and 25 December to the N and SE of the volcano. Weak explosion sounds were heard at the observation post (10 km away) throughout the last 3 weeks of the month. Steady, weak crater glow was seen on 5, 7, 19-20, and 22 December.

"Activity at Crater 3 was similar to that in November. Emissions consisted of weak-to-moderate white-grey vapour-and-ash clouds. Thick grey and brown plumes were forcefully emitted on 1, 6, and 10 December. Blue vapour was also intermittently released. Weak explosion and rumbling noises were heard on the 5th-7th. There was no night glow visible throughout the month.

"Seismicity increased slightly during the month and continued to reflect the eruptive activity at Crater 2. On average, 31 explosion earthquakes/day were recorded . . . ."

"Activity remained at a moderate level in January, very similar to the activity in December. Emissions from Crater 2 consisted of weak-to-moderate white vapour-and-ash clouds. Occasionally, forceful emissions of thick dark-grey ash-laden clouds formed a column several hundred metres high at the summit. Explosion and rumbling sounds usually accompanied these Vulcanian explosions. Fine ashfalls were reported on the SE side of the volcano on a few days. A steady, weak night glow was seen over the crater during the second half of the month, with incandescent Strombolian projections to 100 m on 23-24 January. Activity at Crater 3 was at a very low level throughout the month, consisting only of the gentle release of small volumes of white vapour, with some blue vapour 30-31 January. Seismicity remained low, with only a few explosion earthquakes recorded daily."

"Langila was more active in February than it had been since February-March 1992, with strong, sub-continuous Vulcanian activity from Crater 2, and a few days of eruptive activity at Crater 3.

"Although the volcano was covered in atmospheric clouds for the first week of the month, strong explosion and rumbling sounds from 5 February onward suggested renewed activity. When visible (after the 8th), Crater 2 displayed a dark column of ash-laden vapour that was forcefully released, convoluting and rising ~1 km above the crater. At night on 12 February, incandescent ejecta were visible in the Vulcanian eruption cloud, with ballistic trajectories rising up to 500 m above the crater. The strength of the eruption seemed to decrease after the 12th, with only night glow or mild incandescent projections 15-18 February. During the remainder of the month, Crater 2 released a steady white-gray plume of ash-laden vapour.

"Activity at Crater 3 was mild for the first half of the month, with moderate or weak emission of thin white vapour. Discrete Vulcanian explosions resumed on 12 February. By the 15th, the plume was forcefully rising several hundred meters above the crater. The plume was accompanied by strong explosion sounds and incandescent projections of increasing strength 15-18 February (maximum 400 m above crater). This activity decreased by the next day, with mainly weak white or blue vapour, and only occasional ash-laden emissions on 21-22 and 28 February.

"The seasonal NW wind carried fine ash over villages 8-18 km to the SE. Field inspection showed ~1 mm of ash accumulation in that area."

"Eruptive activity . . . remained at a moderate-to-strong level during March. Crater 2 continued to release white-grey ash-laden vapour at a moderate-to-strong rate and occasional thick dark grey-to-brown ash clouds. These emissions were accompanied by weak-to-loud explosion noises. From the 23rd until the end of the month, continuous dark grey ash clouds rose several hundred meters above the summit. Fine ashfall was reported downwind (SE). These emissions were accompanied by weak explosions and rumbling noises. The summit area was cloud-covered on most nights during the first half of the month. However, incandescent Strombolian projections were visible on the 4th and 5th. On 15, 19-20, and after 23 March until the end of the month, steady weak to occasional bright fluctuating glow was visible. Incandescent Strombolian projections up to 80 m above the summit were seen on the 27th and 29th.

"Activity at Crater 3 was mild during the month, with weak-to-moderate emissions of white and blue vapour accompanied by the occasional forceful ejection of moderate-to-thick dark grey ash clouds rising several hundred meters above the summit. During the last 3 weeks of the month the emissions were accompanied by occasional weak explosion noises. Night glow and incandescent projections were seen on 15, 16, and 19 March.
"A slight increase in seismicity during the month was recorded by the seismograph 9 km N of the volcano. About 200 Vulcanian explosion earthquakes were recorded during the month with the highest daily total of 24 events on both the 23rd and 24th."

"Eruptive activity was at a moderate-to-high level during April. A total of 134 Vulcanian explosion earthquakes was recorded, with the highest daily total of 17 events on 5 April.

"Incandescent Strombolian projections to 300 m above Crater 2 were seen on 2, 4, 5-10, and 23 April. Steady, weak glow was observed on 11, 19, 20, 24, and 26 April. Explosion and rumbling noises were heard throughout the month. Dark grey ash columns and moderate-to-strong white-grey vapour were released every day. Some ashfall to the SE and NW of the volcano was reported.

"Crater 3 was active until 13 April, producing moderate-to-strong ash emissions accompanied by deep explosion noises. Emissions then stopped until 22 April when weak blue and white vapours appeared. Emissions stopped again on 26 April. No glow or incandescent ejections were observed."

"Activity declined to a moderate level in May after about 3 months of relatively strong explosive eruptions. The latest period of incandescent lava ejections and night glow at Crater 2 ended on 9 May, although there were still moderate emissions of thin-to-thick grey ash-vapour clouds. Occasional dark ash columns resulted in light ashfalls on the N and NW sides of the volcano. Weak explosions and low rumbling noises were heard at the beginning of May, but subsided after the 19th. The number of Vulcanian explosion earthquakes recorded in May dropped to 70, compared to 134 in April. Activity from Crater 3 consisted of weak white vapour emissions. No glow was observed, and the crater remained silent."

"Activity declined to a low level in June and remained low through July. Crater 2 intermittently released white-grey ash and vapour clouds in small to moderate amounts. The crater was silent throughout the month, as it has been since the end of May (BGVN 18:05). No glow was observed. The number of Vulcanian explosion earthquakes showed a marked decline to 19 in June from 70 in May and 134 in April. Crater 3 continued to occasionally release weak emissions of white vapour. No activity was recorded from Crater 3 in July.

"Langila's activity increased slightly in August. Crater 2 released white-grey vapour and ash for most of the month. Explosions producing ash falls in inhabited areas were recorded on 6, 8, 20, and 25-26 July. Crater 3 emissions consisted of weak blue vapour.

"Activity appeared to decline in September. Crater 2 emitted weak to moderate amounts of vapour and ash. On a few occasions, falls of ash took place in inhabited areas about 10 km downwind from the vent. Activity at Crater 3 continued at a low level with weak emissions of white and blue vapours. Seismicity was low throughout the month."

"After 5 months of mild activity, stronger eruptions resumed in mid-October from both Craters 2 and 3. During the first weeks of the month, activity at Crater 2 consisted of occasional Vulcanian explosions rising to a few hundred metres above the crater and causing minor ash fall at the summit area. Crater 3 released weak, thin white and blue vapours.

"By 15 October, ash-laden emissions from Crater 2 became continuous. On the 17th, rumbling noises and bright night glow indicated a return to more sustained eruptive activity. The next day, Crater 3 released grey ash and incandescent lava clots to a height of 20 m, with continuous rumbling sounds. The eruptions from both craters remained moderate, more Vulcanian at Crater 2 and more Strombolian at Crater 3. Night glow was not observed at Crater 2 after the 24th, although dark ash emission persisted. Loud Strombolian explosions occurred at Crater 3, although incandescent ejections remained small. On the 30th, a lava flow emerged from the W side of Crater 3 and progressed northward, in a dry stream channel, on the W side of the lava field at the N foot of the volcano. The following night, Strombolian ejections reached 100 m above the crater rim. A particularly large Vulcanian explosion on the afternoon of 31 October produced a dark column that rose to ~10 km.

"Both seismographs were unoperational before 28 October. From that day onward, the level of seismicity was relatively high, with up to 44 explosion events/day."

[Volcanism] continued during November at more moderate levels. Activity from Crater 2 consisted of moderate Vulcanian explosions accompanied by loud detonations. Some of these ash-laden emissions rose several hundred metres above the crater rim producing light ashfalls on the N and NW sides of the volcano. Steady weak red glow from Crater 2 was observed on 15, 21, 22, and 23 November. In the first week of November, Crater 3 activity consisted of weak-to-moderate Strombolian explosions and weak lava effusion. After the 7th, the activity changed to Vulcanian explosions only, accompanied by weak-to-loud detonations. Seismicity showed a moderate level of activity with 1-46 recorded explosion events/day."

"The moderate eruptive activity . . . continued unabated in December. Both craters erupted spasmodically throughout the month, generating moderate volumes of ash. The activity may have been stronger at Crater 3 judging by the reported loud explosions there and ejections of incandescent lava-fragments that were seen on a few nights at mid-month. By contrast, Crater 2 explosions were muffled and only glow above the crater was seen at night. Seismicity was dominated by explosion events at rates of up to ~40/day."

"Both craters continued their spasmodic Vulcanian eruptions throughout January, generating moderate volumes of ash. Activity was stronger at Crater 3; explosions were heard intermittently and produced ash clouds rising a few hundred meters above the crater before being dispersed. In contrast, Crater 2 explosions were muffled and ash emission less frequent. Being the rainy season, the craters were covered by atmospheric clouds on most nights, but incandescent projections were seen at Crater 3 on 3 January. A steady red glow above Crater 2 was seen on 3 and 30 January. Seismic activity was relatively high, with up to 76 explosion events/day . . . ."

"Crater 3 continued to produce mild spasmodic eruptions while Crater 2 activity was at a low level. During the first week of February, loud explosions at Crater 3 accompanied the release of grey ash, moderate to thin in volume, that rose several hundred metres above the summit. The intensity of explosions during the rest of the month was much lower, but the amount of ash emitted remained steady. Night glows were not observed from Crater 3, although it was often obscured by atmospheric clouds. Crater 2 activity was low during most of the month with the release of thin pale grey ash. From 7 to 10 February there were forceful emissions of moderately thick grey ash. Weak crater glow was seen on a few nights when the summit was clear of atmospheric clouds. Seismic activity during February remained at a moderate level with minor fluctuations."

"Crater 2 and Crater 3 both produced mild spasmodic eruptions. Crater 2 released small volumes of ash during 11-18 March, accompanied by deep roaring sounds and incandescent projections on the 15th and 16th. Crater 3 generated occasional explosion noises during 1-10 March, and released small volumes of ash on 3, 10, 13, 15, 17, 27, and 29 March. The ash emissions on 15 March were accompanied by loud explosion noises and incandescent projections. Low explosion noises were also heard on the 29th. There was no seismic monitoring at Langila in March."

"Observations were conducted during 1-17 and 23-27 April. The level of activity was slightly lower than in March. Emissions from Crater 2 consisted mainly of thin-to-moderate white-grey vapour-and-ash clouds. Explosion noises were heard on 4, 5, and 17 April, and weak rumbling noises were heard during 23-27 April. The explosion on 4 April produced a thick ash column that rose a few hundred metres above the crater and resulted in fine ashfall on the NW side of the volcano. Steady weak red glow was observed on 23-24 April. Crater 3 released emissions of thin white vapour with occasional low ash content. Seismic activity was at a low level."

Both craters at Langila continued at a low activity level in May. Emissions from Crater 2 consisted of weak-to-moderate white-gray vapour and ash clouds. Occasional forceful ejections of thick, dark-grey ash columns accompanied by explosion noises were reported on the 2nd, 7th, 9th, 20th, 29th, and 31st. Fine ashfall was reported on the 2nd and 20th on the NW side of the volcano. A steady weak red glow was visible on the 5th. Crater 3 released thin white vapour with very low ash content accompanied by thin blue vapor. Seismic activity was at a low level at the beginning of the month. No seismic recording was achieved after the 3rd because of equipment failure."

"The relatively low level of activity . . . continued throughout June. Emissions from Crater 2 consisted of weak-to-moderate white-grey vapour-and-ash clouds, associated with blue vapour on the 15th only. Forceful ejections of thick grey ash columns rising several hundred metres above the crater rim were reported on 1, 6, and 8 June. These emissions resulted in fine ashfalls NW and SE of the volcano. On these occasions, as on most days after 16 June, weak explosion noises were heard. Steady weak red glow was visible from the 6th until month's end.

"Crater 3 released thin white vapour with very low ash content, and occasionally thin blue vapour. On 27 June, a moderately thick white-grey ash column rose to a few hundred metres above the summit and dispersed fine ash to the NW side of the volcano. It was accompanied by one deep explosion at 0901. There was no visible glow throughout the month.

"Seismographs were unfortunately faulty until 29 June. When back in operation, they recorded a low level of activity comparable to that of early May."

"Eruptive activity at Crater 2 continued during July, while Crater 3 activity was at a low level. Throughout the month, Crater 2's normal moderate emissions of thin white-grey vapour were disrupted by forceful ejections of thick, mushroom-shaped, grey-brown ash clouds accompanied by low explosion and rumbling sounds. These caused fine ashfall NW of the volcano. On 16 and 22 July, the ash clouds rose several thousands of meters above the crater. Steady weak night glow was reported on 26 July and there was fluctuating weak-bright glow on the 29th. Crater 3 continued to emit small volumes of mostly white vapour, sometimes with blue and grey vapour. There were no audible sounds or night glow reported during July. Seismic activity throughout the month remained at a low level with between 1 and 7 small low-frequency earthquakes/day."

"Eruptive activity at Crater 2 continued in August. Except for a quiet period during 1-11 August, on most days thick columns of mushroom-shaped grey-brown ash clouds were released. Light ashfall in coastal areas downwind was reported on 12 and 26 August. One explosion noise was heard on the 12th, and occasional rumbling noises were heard on the 17th and 23rd. Steady weak red glow was seen on 1 and 15 August.

"Crater 3 activity was generally low. Throughout August, Crater 3 produced weak emissions of thin, pale-grey and occasionally blue vapour. After the 26th the volume of blue emissions became moderate. The 30th marked the beginning of occasional moderate to thick emissions of grey-brown ash clouds producing light ash fall on the N and NW sides of the volcano.

"Seismicity was low throughout the month. Daily totals of volcanic earthquakes were between 1 and 5."

Eruptive activity in September and October at both craters consisted of moderate and intermittent Vulcanian explosions. Crater 3 was active during the first nine days of the month. It released a moderately thick vapor plume, with occasional dark gray ash clouds, accompanied by explosions and rumbling sounds, and resulting in light ash falls onto the NW flank and coastal villages. For the remainder of September and October, it only emitted very thin wisps of vapor, occasionally accompanied by blue vapor.

At Crater 2, background levels of moderate white and blue vapour emissions continued, and very weak night glow was seen on 7 September. However, activity picked up on the 12th and 13th with occasional dark ash-laden, convoluting Vulcanian explosions. Similar low-level eruptive activity resumed on 15-18, 24, and 28-29 September.

A good correlation could be seen between the level of seismicity and volcanic activity in September. The two local seismographs recorded 2-5 explosive events/day during 1-9 September at Crater 3, and then 2-8 events/day during each of the intermittent phases of activity at Crater 2. Seismicity remained at a low level throughout October.

"Continuing the trend of previous months, eruptive activity consisted of moderate and intermittent Vulcanian explosions from Crater 2. During most of November, activity at Crater 2 consisted of noiseless emission of thin white vapour. Occasionally (on 4, 6-8, 15, 18, and 27-29 November), weak explosions were heard and accompanied the rise of dark-grey ash-laden columns to a few hundred meters above the crater. Some of these explosions were large enough to be recorded by a seismometer 9 km away. Fine ashfall was reported in downwind coastal areas. Between 14 and 27 November, weak night glow was seen and the activity was accompanied by low to loud rumblings. Crater 3 released only fumarolic emissions, occasionally accompanied by blue vapour."

"The eruptive activity . . . declined in the first half of December. There were a few Vulcanian explosions from Crater 2 in the first half of the month, and virtually no activity during the second half of the month. Crater 3 continued to release only fumarolic emissions, with occasional wisps of blue vapour. Seismicity remained low throughout the month.

"Activity at Crater 2 in the first two weeks consisted mainly of weak-moderate emissions of white-grey vapour. Roaring and rumbling sounds were heard on 2 and 3 December; fluctuating glow was observed at night. A deep explosion heard on 7 December generated an ash column several hundreds of metres above the crater rim; there was fine ashfall to the SE. During 10-13 December there were occasional rumbling, roaring, and explosion noises, and steady weak glow was seen on 10 and 13 December. From 14 December until the end of the month, no sounds were heard and weak to moderate emissions again consisted of white-grey vapour. Steady weak night glow was seen on 23, 28, 29, and 31 December."

"Emissions at Crater 2 consisted mainly of white-grey vapour-and-ash clouds in low-moderate volumes. Fine ashfall to the SE of the volcano was reported on 3 January. Occasional rumbling noises accompanying the emissions were heard intermittently throughout the month. Low-loud explosions were heard on 3, 30, and 31 January. A weak glow was seen on most nights during the first week and on 21 and 30 January around the crater rim. Activity at Crater 3 was mostly confined to weak-moderate emissions of white vapour accompanied by pale grey ash clouds and wisps of blue vapour on 26 and 28 January. The seismograph was not operational during January."

"Activity during February continued to be focused at Crater 2, at the moderately low level observed since December. Emissions consisted mainly of white-to-grey vapour-and-ash clouds in low or moderate volumes. Occasionally, an explosion produced a larger and darker cloud that rose a few hundred meters above the crater and produced fine ashfall SE of the volcano. Rumbling noises accompanying the emissions were heard intermittently throughout the month, and weak glow was seen on most clear nights. Activity at Crater 3 consisted essentially of fumarolic emission of thin white vapour. The seismograph was not in operation during February."

"Monitoring was temporarily discontinued on 18 March. Until that time activity at Crater 2 was at a moderate level, similar to that observed in February, while Crater 3 showed a low level of activity. Emissions from Crater 2 were mostly white vapour, weak to moderate in volume. Occasionally grey ash clouds were emitted. Light ash fall took place around the crater. One loud explosion was heard on 8 March with weak explosions on the following two days and low rumbling sounds on the 16th. Steady weak night glow was observed on 16 and 17 March. Crater 3 released very thin to occasionally moderately thick white vapour. Thin blue vapour was observed on 1 and 7 March. There were no audible sounds and no night glows. Both seismographs remained inoperative throughout the month."

Monitoring of Langila resumed on 3 April following a lapse from 18 March to 2 April. Up to that time, activity at Crater 3 remained low and activity at Crater 2 continued at a moderate level. After the lapse in monitoring, Crater 2 continued to emit white vapors in low to moderate volumes. Gray ash clouds were occasionally emitted to several hundred meters above the crater. Occasional rumbling sounds and night time glows were normally associated with the ash emissions. Loud explosions were heard on 3 and 30 April. Ashfall NW of the volcano (in the Kilenge area) was reported on 11 April. Crater 3 released thin white vapor accompanied by wisps of blue vapor on 12, 14, 21, and 27 April. There were neither audible sounds nor night glows. Both seismographs remained inoperative during the month.

"Throughout May, Crater 2 produced forceful moderate to strong emissions of white-grey vapour and ash as well as occasional dark mushroom-shaped ash clouds. Many of the ash clouds rose several hundred metres above the crater rim, resulting in light ashfall to the N and NW on most days of the month. Some of the forceful ash emissions were accompanied by weak (and occasionally strong) detonations, but more frequently by rumbling noises. A strong explosion on the 26th was accompanied by lighting flashes. Projections of red incandescent lava fragments were observed on the 9th and 26th, and weak red summit glows were observed on 3, 23, 25, and 28-29 May. Activity at Crater 3 was at a very low level, mainly gentle emissions of thin white vapour. There were some days when no vapour emissions were observed. Neither audible noises nor summit glow were noted. One seismograph was restored and began operating again on 29 May."

Eruptive activity was centered at Crater 2 throughout the month, and maintained a moderate level slightly lower than in May. These continuous to sub-continuous emissions were accompanied by occasional forceful, mushroom-shaped, light gray to brown ash clouds rising several hundreds of meters above the crater rim. Fine ashfalls extended ~10-15 km from the volcano to the N and NW coasts. Weak deep explosion and rumbling sounds were heard on 13, 20, 22, 23, and 30 June, with weak summit glow seen only on 30 June.

Activity at Crater 3 remained very quiet throughout the month although thin white vapor wisps were observed on 11, 14, and 27 June. Neither audible noises nor summit glow were noted. Throughout June no seismicity was recorded.

Moderate eruptive activity continued at Crater 2 throughout July; intermittent large explosions alternated with weaker ash and vapor emissions. The larger explosions rose several hundred meters above the crater rim, dropping ash on the downwind (N-NW) side of the volcano. The sounds from these large explosions ranged from loud detonations to deep rumblings. Crater glow was observed on 1 and 16 July. Activity at Crater 3 remained very low, with only weak white vapor emissions. The seismograph was inoperable throughout the month.

Located on the N coast of western New Britain, Langila consists of four overlapping composite cones. These cones lie on the E side of the inactive Talawe volcano. An extensive lava field extends from the cones toward the coast. Langila is one of New Britain's most active volcanoes.

During August, intermittent Vulcanian explosions interspersed with weaker ash-and-vapor emissions continued at Crater 2. Larger explosions rose several hundred meters above the crater rim and resulted in ashfalls on the downwind (N-NW) side of the volcano. Observers heard low detonations to deep rumblings; on 4, 5, and 17 August they saw weak, steady crater glow. No activity was seen from Crater 3. The seismographs remained inoperative in August.

The increased eruptive activity at Crater 2 that began during late September continued throughout October. The activity was marked by intermittent audible explosions. The bigger explosions developed plumes that rose several hundred meters above the summit crater, resulting in ashfalls on the volcano's N-NW side. Langila produced steady but weak crater glow on most nights during October; it threw incandescent lava fragments on 23-24, 26, and 31 October. Crater 3 was quiet, only giving off weak white emissions towards late October. Seismic recording restarted on 5 October after both seismographs had been inoperative since January 1995. October seismic activity was moderate.

Throughout November-December, Crater 2 continued to emit white-to-gray ash and vapor, with plumes rising up to several hundred meters above the crater. During November, ashfalls reached 10-15 km on the N-NW flank; these eruptions were accompanied by audible explosions and rumbling. The eruptions threw incandescent projectiles during the first half of both November and December, and steady crater glow took place on most November nights and on 9-11 December. Crater 3 remained quiet. The greatest December activity, during the 23rd through the 26th, had emissions similar to those in November, but plumes rose somewhat higher (up to 1 km above the crater) and ash fell 10-15 km SE and SW.

Activity at Crater 2 was low to moderate in January and moderate in February. During this time, the explosions produced thick white-gray ash-and-vapor clouds; these usually blew SE over unpopulated areas. Eruption sounds varied between rumblings and detonations. On most February nights, observers saw variable glow over Crater 2 and, on 2, 8, and 23 February, ejection of incandescent lava fragments. During January and February, Crater 3 was inactive, but moderate seismicity prevailed. The daily total of explosion earthquakes during February ranged between 0 and 5.

Moderate explosive activity continued at Crater 2 during March, however, there was possibly a slight decline compared to last September. Intermittent Vulcanian explosions released ash clouds that rose several hundred meters above the crater. These explosions resulted in minor ashfalls to the volcano's SE. A weak but steady crater-glow was observed on a few nights. In accord with these observations, 6-30 daily explosion earthquakes registered at a station 4 km away. There was no visible activity from Crater 3.

Moderate eruptive activity continued at Crater 2 during April. As in recent months, the activity consisted of intermittent moderate Vulcanian explosions that produced variable density, white-to-gray ash-and-vapor clouds rising several hundred meters above the rim. The clouds were blown to the N, NW, and SE of the volcano, resulting in fine ashfalls. Occasional eruption sounds consisted of explosion noises and rumblings throughout the month. Crater-glow of variable intensity was seen on most nights during the month. The seismic station 4 km from the volcano registered a daily range of 10-40 explosion earthquakes. Crater 3 was quiet during the month.

Crater 2 activity continued in May as in past months (BGVN 21:04) with intermittent Vulcanian explosions producing thin-to-thick white-to-gray/brown ash-and-vapor clouds. These clouds rose several hundred meters above the rim before being blown to the N, NW, and SE and producing fine ashfalls. Occasional explosions were heard. Glows of variable intensity were seen on most nights during the first three weeks. Weak projections of incandescent lava fragments were observed on 12 and 14 May. A daily range of 10-50 explosion earthquakes was recorded at the seismic station until it became non-operational on 24 May. Crater 3 remained quiet apart from a single emission of very thin white/gray vapor on 7 May.

During June, white-gray or brown ash and vapor clouds emitted from Crater 2 rose to several hundred meters above the crater rim. Fine ash was mostly blown to the NW and occasionally to the SE and NE. Rumbling noises were heard throughout the month. During the first half of June, night glow was seen only on 5 June, but weak red glow was observed on most nights of the second half of the month. Weak to moderate projections of glowing lava fragments were observed on the nights of 17, 18, 19, and 21 June. Crater 3 remained quiet during June.

During July, Crater 2 continued its low-level eruptive activity and Crater 3 remained quiet. Crater 2 emitted gray to brown ash clouds, which rose several hundred meters above the crater. The ash clouds were blown to the NW and produced light ashfall. The emissions were accompanied by rumbling and explosion sounds. On most nights in July, variable glows were observed around the crater. Small incandescent lava fragments were ejected on 12 July.

Although there was a lull in activity at mid-month, mild eruptive activity continued at Crater 2 in August. Moderate intensity, frequent ash emissions accompanied by rumbling and detonations took place from the beginning of the month until the 14th. In the period 15-20 August, the emissions were usually only white vapor. However, on the 16th there were two explosions. Frequent ash emissions resumed on the 21st with occasional stronger explosions. Throughout the month there were sightings at night of steady weak red glow above the crater. The Langila seismographs remained inoperative in August.

Crater 3 remained quiet during September. Moderate Vulcanian activity at Crater 2 continued until 14 September; after then the activity declined to weak emissions of thin, white vapor. Emissions from Crater 2 produced thin white to thick gray vapor-and-ash clouds, which rose to a few hundred meters above the crater rim. Ash-laden emissions were commonly accompanied by low rumbling sounds. On 4-6, 10, and 13-14 September, strong explosions resulted in light ashfall on populated areas to the NW. Weak, steady crater glows were observed on most nights before 14 September. The Langila seismographs were inoperative during September.

Eruptive activity at Crater 2 continued during October-December. The activity pattern of 7-26 October was similar to that during January-September. Emissions included thin, white to thick, gray vapor-and-ash clouds. The ash clouds rose ~1-2 km above the crater. Ashfall was observed on 8-22 October on the N, NW, and SE sides of the volcano. Weak, steady, red glows were seen on the nights of 7, 12-13, 20-21, and 26 October. Projections of red incandescent lava fragments occurred on the nights of 8-10 and 17 October. After 26 October eruptive activity declined to emissions of thin, weak, white vapor. During November and December, activity at Crater 2 consisted of emissions of thin, weak, white vapor, and, occasionally, moderate ash clouds. Light ashfall was observed on 5 and 11-12 November on the N, NW, and SE sides of the volcano.

Crater 3 remained quiet during October-December. Thin, weak, white vapor began to emit on 1 December. Seismic monitoring was conducted only between 11 November and 4 December. Seismicity was low during this period.

Throughout January activity at Crater 2 continued at a low level. Although on most days, Crater 2 only occasionally released pale gray ash clouds, from 9 to 19 January, darker gray clouds were emitted. These were occasionally accompanied by weak rumbling sounds and the emission of glowing lava fragments. The ash clouds seldom rose higher than ~2.5 km, although they occasionally reached ~4 km altitude. They blew to the SE, resulting in light ashfall. During January, Crater 3 released only fumarolic white vapors. No seismic recording took place during the month.

During 11-12 February at least five aviation reports gave warnings to pilots (SIGMETs) for Langila's plumes. The reports indicated the plumes reached at least 10.7 km altitude on 11-12 February. Although some reports described W-drifting plumes, one report at 1745 on 12 February described a "tight radius" plume that consisted of a ". . . solid core of discernible ash up to [10.7 km altitude]."

Crater 3 remained quiet during February, but Crater 2 continued to generate Vulcanian explosions; in some cases ash columns rose to 6 km. During early February observers noted loud detonations, roaring, and rumbling. About mid-month bad weather obscured the volcano. From 21 February until the end of the month the explosions seemed weaker. During February there was no seismic recording.

Aviation sources reported ash plumes on 11-12 February (BGVN 22:01) to at least 10.5 km altitude. Since then, Tom Casadevall learned of an aircraft encounter with an ash cloud that was presumably from Langila. The commercial 747 was en route on R-204 from Seoul to Brisbane. The encounter, 1129 GMT on 12 February, occurred at an altitude of ~11 km (37,000 feet) at a location [~550 km SSW of Langila, near 8.75°S, 144.5°E]. The aviator's observations follow.

"Outside air temp[erature] was at -48°C, suddenly [outside air temperature] increased to - 38°C. Smell of sulfur was experienced in the cockpit. No change in engine parameters. Crew attempted to contact [air traffic control] to change course, but were unable to make radio connection due to poor signal. After 5 minutes, flight exited dust cloud and continued on to Brisbane. Safe and uneventful landing. Upon aircraft return to Seoul, all engines were inspected per [Airline Maintenance Manual] for volcanic ash ingestion. Inspection reports found no evidence of problems."

Volcanic ash plumes pose hazards to aircraft; for example, the ash, which is not discriminated from weather clouds by on-aircraft instruments, can seriously damage jet engines.

Although visibility was limited by a cyclonic depression during much of March, on the 22nd an ash plume rose to 3 km. Then, during the first ten days of April a brief lull took place as Crater 2 typically issued moderate volumes of white vapor and produced isolated weak explosions.

Between 11 and 16 April, ash emissions became more frequent. During 17-20 April, emissions consisted of continuous, thick pale brown to dark gray clouds. For the remainder of the month the emissions occasionally consisted of thin to thick ash of pale brown to pale gray color.

Crater 3 exhibited weak fumarolic activity in April. The seismographs were inoperative during March and April.

Vulcanian explosions resumed in late May. During the first 3 weeks of the month Crater 2 released moderate volumes of steam. Then, an explosion on the 22nd at 1510 produced dark gray ash clouds that rose to about 4.5 km above the crater rim. Explosions on the following days of May generated ash clouds to heights of between 2 and 3.5 km. Low rumbling sounds on the 27th presumably accompanied other explosions. Only weak vapor vented at Crater 3 during May. Seismographs remained inoperative.

Mild Vulcanian activity prevailed at Crater 2 in late May and this continued in June. Except for 5-9 June, throughout the rest of the month Crater 2 emitted moderate, pale to dark- gray ash clouds. Some rose ~2.0 km above the summit. Fine ash fell on the N and NW parts of the volcano on the 10, 12 and 18 June. Occasional low rumbling noises were heard on 13, 15, 16, 19, 20, 22, 28, and 30 June. No glow was observed. As has been typical, Crater 3 remained quiet. Seismographs remained inoperative during June.

Although Crater 3 remained quiet and seismographs remained inoperative during July, moderate Vulcanian explosions continued at Crater 2. Throughout the month, Crater 2 produced gray ash clouds rising ~2 km above the summit. Fine ash fell on the N and NW parts of the volcano. On the night of 2 July observers saw incandescent lava projections; during 4-9 July there were weak explosions and roaring noises. Large explosions on 29 July produced dark gray ash clouds that rose ~5 km before drifting NW. Previously, on 22 March, aviators noted Langila ash clouds to 3-km altitude.

Throughout the month Crater 2 produced occasional gentle emissions of pale gray to brown ash clouds, generally low in ash content. There were single Vulcanian explosions on 3, 4, 14, and 19 August that were accompanied by forceful emissions of dark gray ash clouds that rose to ~3,000 m above the summit. Ash clouds were blown NW, producing light ashfalls at settlements 11 km from the volcano. Crater 3 remained quiet throughout August. There was no seismic recording during the month.

At Crater 2, vapor and ash were emitted throughout the month. On the 14th an ash column rose to ~2 km and caused some local ash falls. No activity was reported from Crater 3. The seismographs were inoperative throughout the month.

Crater 2 released white and blue vapors during 1-18 October; from 6 to 9 October the emissions were accompanied by weak rumbling noises. On 19 October, mild Vulcanian activity resumed at Crater 2, but Crater 3 remained quiet throughout the month. Emissions from Crater 2 during 19-31 October consisted of thin white to thick gray vapor and ash clouds that rose a few hundred meters above the crater rim; low rumbling noises were observed during the ash emissions.

A 25 October explosion produced a thick dark gray ash cloud that rose ~2,000 m above the summit and resulted in light ashfall NW of the volcano. Weak steady night glow was visible on 24 and 29 October.

Seismic recording resumed on 25 October; due to problems with the equipment, recording had not occurred since May 1996. Seismic activity was low during 25-31 October.

Occasional explosions occurred during December at two of Langila's craters. Moderately thick gray ash was emitted from Crater 2 through most of the month, accompanied by deep roaring and rumbling sounds. An ashfall was reported on 5 December. Weak but steady and sometimes bright fluctuating night glows were visible on 4, 25, and 26 December. Crater 3 released weak fumarolic vapors. Neither seismograph was operational during December.

Langila was relatively quiet throughout January. Crater 2 generally released weak to moderate emissions of white vapor, but on 10, 11, 17, 18, 20, and 21 January, weak pale-gray ash was emitted. Crater 3's activity consisted of gentle fumarolic emissions. Both craters were noiseless throughout the month and no glow was observed. The seismograph remained out of order.

Throughout February, there was intermittent weak eruptive activity at Langila's Crater 2 while Crater 3 remained quiet. On the 3rd, two loud explosions were heard that produced thick dark ash clouds rising 2,500 m above the crater. A similar explosion occurred on 5 February. During 6-14 and 24-26 February, Crater 2 discharged small- to moderate-sized gray ash clouds. Low roaring and rumbling sounds were heard on the 20th, 22nd, and 24th. Crater 3 was restricted to weak fumarolic emissions the entire month. Both seismographs remained inoperative.

Moderately thick white vapor emissions continued at Crater 2 in April. Gray ash-laden clouds were seen rising to altitudes of 1-1.5 km on 7, 9-12, 16-17, and 22 April. On 25 April, ash clouds rose to an altitude of 2.5 km. A weak incandescent glow was seen on 22 and 28 April. Crater 3 released weak fumarolic vapors.

Langila remained comparatively quiet during May and June. Direct radio communication to RVO had been a persistent problem, but reports were relayed by ships operating in the area.

Crater 2 continued weak-to-moderate emissions of white vapor during both months. During 9, 13, 17, and 19-21 May a blue vapor accompanied the usual white vapor. Occasional gray ash emissions were observed on 10 May, and 16, 22-24, 27, 29-30 June. Weak glow from the crater was seen on the nights of 2 and 3 May, and 16 and 29 June.

Crater 3 only released weak white fumarolic vapors. The seismograph remained non-operational during May and June.

During July, Crater 2 continued to release weak-to-moderate white vapor with occasional pale-gray ash. During 13-15 and 29 July the pale gray ash emissions changed to dark gray ash clouds that rose 2,000-2,500 m above the summit. Low roaring noises were heard 4-6, 8-9, and 16 July. No activity was reported from Crater 3 during July, and no glow was observed at either crater throughout the month.

During August both Crater 2 and 3 released low-to-moderate volumes of white vapor. There were also small amounts of blue vapor seen at Crater 2. One loud roaring and rumbling sound was heard at Crater 2 on 28 July accompanied by the emission of a dark-gray ash-laden cloud rising 1,000-2,000 m above the summit. This cloud was blown to the NW. The seismograph remained inoperative throughout July and August.

Crater 2 emitted thin to thick white vapor throughout September, with an occasional ash component. Weak roaring noises were reported on 1 September. One large explosion on 21 September sent ash to an altitude of 2-3 km and resulted in ashfalls to the SW. Crater 3 was quiet, emitting only thin white vapor.

The activity at Crater 2 during October was moderate and uneventful. Pale gray ash clouds rose intermittently to ~500 m, without sound. On 21 October, however, weak roaring and rumbling sounds accompanied emissions to 1,000-1,500 m and a bright fluctuating night glow.

The ongoing Vulcanian eruption at Crater 2 continued throughout November and December. Emissions consisted chiefly of gray ash clouds that drifted SW, resulting in fine ashfall. On 2 November a significant ash column was ejected forcefully up to ~2 km above the crater. Emissions during November were sometimes accompanied by roaring and rumbling sounds. No night glow was reported.

Mild, intermittent, eruptive activity continued at Crater 2 in January, while Crater 3 remained quiet. Crater 2 emitted continuous white vapor with occasional mild emissions of pale gray to brown ash clouds. During 1-4 January most ash emissions were accompanied by low rumbling and roaring sounds. The emissions rose to about 500 m above the summit before blowing to the SE. There was no seismic recording during the month.

Crater 2 continued to display irregular Vulcanian eruptive activity and pale gray ash emissions. Crater 3 remained quiet. During March the ash plumes rose to 500-2,000 m above the summit before being blown NW. Variable winds in April caused the ash plumes to be blown to the NW, NE, and SE.

Crater 2 exhibited mild, continuous volcanic activity during May and very low activity during June. The May activity primarily consisted of the escape of moderately thick gray to brown ash clouds. Weak rumbling and roaring noises occasionally accompanied the emissions and fairly significant ash columns were forcefully ejected to 2 km height on 4, 9, 11, and 30 May. The ash clouds drifted NW, resulting in downwind ashfall. The June activity was summarized as the escape of mostly small to moderate amounts of vapor. Occasional ash-bearing (gray-brown) ash clouds were seen. In both months, there was no visible night glow, Crater 3 remained quiet and only occasionally released thin white vapor. The seismograph remained inoperative.

No noise or night glow was reported from any vent during August and activity was very low in September and October. Throughout this period varying amounts of white vapor were observed from Craters 2 and 3. A blue component was observed in the vapors emitted from Crater 2 on the mornings of 4 and 5 August, whereas light to moderate ash emissions occurred on 6 and 7 August. On the morning of the 10th, ash was forcibly ejected 500-1,000 m above the crater rim. Only white vapor was emitted until the end of the month except on 25, 29, and 31 August when a light ash component was reported. On 21 and 30 September forceful emissions of thick brown ash were observed rising ~2 km above the summit from Crater 2. Such occasional forceful emissions continued into the first few days of October. The ash clouds rose 500-1,000 m above the summit and were later blown N. After that the emissions reduced to thin to thick white vapor.

Intermittent Vulcanian eruptive activity at Crater 2 continued throughout November. Crater 2 released small-to- moderate volumes of gray ash clouds on 2, 4, 9-17, 20, and 25-27 November. On the 25th, two explosions produced dense convoluted ash clouds that rose ~1.5 km above the crater, resulting in fine ashfall downwind to the SSE. A bright red glow was visible on the 15th. Crater 3 was quiet throughout the month. Visual observation reports in December were only received on the 1st and 2nd. On these two days the activity at both craters was low, producing very weak volumes of white vapor. The seismograph remained unoperational.

Activity remained at a low level during 1-20 January and no unusual volcanism was reported for February or March. Reports were absent for 21-31 January, but earlier in the month Crater 2 released weak thin-to-thick white vapor in moderate volumes. On 3-6, 19, and 20 January the emissions included weak gray and brown ash clouds. Crater 3 released weak white vapor throughout the month. The seismograph remained non-operational.

Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano sits NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (Crater 3) was formed in 1960 and has a diameter of 150 m. The Cape Gloucester observation post, airstrip, and seismometer is 9 km N of the volcano.

This report covers April through June 2000. Activity remained at a low level in April. From visual observation reports received only up to 9 April, Crater 2 periodically gently released moderate to thick ash clouds. However, on 5 and 9 April, the ash clouds were released more forcefully and with rumbling sounds. These ash clouds rose 1-2 km above the summit before being blown SE. Crater 3 released light white vapor throughout the month.

Visual observations were next reported after 16 June. Crater 2 produced thick, white ash clouds in moderate volume. On 23 and 24 June, these clouds were accompanied by blue vapor. On 16 and 18 June, rumbling noises were heard. Crater 3 was inactive in June with the exception of a weak trail of thin white vapor escaping on 16 June.

The seismograph remained non-operational throughout the entire reporting period.

The mild Vulcanian eruptive activity that occurred at Langila's Crater 2 through June 2000 (BGVN 25:07) continued during July-October 2000. In addition, low-level volcanic activity continued at Crater 3. No reports of unusual activity were submitted during July and August.

During September, intermittent, mild Vulcanian activity occurred at Crater 2. The activity consisted of moderate emissions of thin-to-thick white vapor, which were occasionally accompanied by gray ash clouds. On 21, 25, and 30 September thick, dark gray, convoluting ash clouds were forcefully released, rose 200 m above the summit, blew to the N and NW, and deposited fine ash. On 7, 9-11, and 27 September wisps of blue vapor accompanied the emissions. During the month volcanic activity was low at Crater 3, with only thin white vapor sporadically visible.

Through October intermittent, mild Vulcanian eruptions continued at Crater 2. The vent usually emitted white vapor, which was sometimes accompanied by a blue tinge and occasionally by a light ash component. On 8 October a forceful emission of thick ash rose to 1 km above the crater rim. This heralded a few days of increased ash emissions, with some forcefully expelled light gray/brown clouds on the 15th. During 16-24 October continuous white vapor emissions with a small ash component were common. At 0801 on 24 October a dark gray-to-black ash column rose 1 km above the crater rim. On 25 October an ash cloud that rose to 2 km above the crater deposited ash toward the N. Likewise, at 0655 on 26 October a thick, white vapor plume was accompanied by an ash column that rose to 1 km above the crater rim. The ash emissions continued throughout the day, and similar activity occurred the next day. For the rest of the month activity was confined to white vapor with an occasional ash component. During October varying amounts of white fume were emitted from Crater 3. Throughout the period there were no reports of noises or night glow at the volcano; the seismograph remained out of operation.

Based on information from a pilot report, the Darwin Volcanic Ash Advisory Center (VAAC) reported that an ash cloud from Langila was observed on 11 July 2002 at about 0900 and rose to a height of ~3.4 km. No ash was identifiable on satellite imagery. This was the first reported activity since October 2000 (BGVN 25:11). RVO noted that the observatory at Langila was broken into in 2000 and had its radio stolen. There are no telephones nearby, and since then they have had to rely on mailed reports (very infrequent), reports from pilots, and the Darwin VAAC.

MODVOLC Thermal Alerts, 2001-2002. MODIS thermal alerts occurred on 25 May, 19 and 26 June, 12-15, 24, and 26 August, and 13 October 2002; there were no alerts in 2001. The largest number of alert pixels was 3 on 14 August. The highest alert ratio was -0.648 on 24 August. Putting these two together suggests the most intense activity in mid-late August, but this could be severely biased by cloudy days. Available maps do not allow an accurate location of the summit, and are not of a scale to provide accurate registration. However, all but one of the alert pixels are within ~1 km of each other so there appears to be a spatially restricted event consistent with a short flow (less than a few hundred meters long) or a small dome or incandescent vent a few tens of meters across, which would affect more than one pixel when the pixel boundary fell across, or very close to, the flow, dome, or vent. Both recently active craters (Crater 1 and Crater 2) are also within a 1-km area, along a NE-SW trend, similar to the orientation of the alert pixels.

The summit area was obscured by rain and clouds on many days in January and February. During clear days (4-5, 8-16, 18-21, and 25 January; 1-9 and 13-17 February), Crater 2 released weak to moderate emissions of white and white-gray vapor. Occasional ash-laden gray-brown and forceful dark gray emissions were produced on 10 and 14 January, respectively. The forceful emissions on the 14th were accompanied by low roaring noises. On 18 January a large explosion produced a thick dark ash column that penetrated the atmospheric clouds over the summit area. Occasional white-gray and gray-brown ash-laden emissions were observed on 1-6 February. On 3 and 4 February the same vent forcefully ejected dark gray ash clouds. Night glow was observed at Crater 2 on 14 and 15 January; some of the glow on the 15th changed into weak incandescent lava projections. Variable weak to bright red glow was observed at night on 3-6 and 14 February. On 3 February the glow fluctuated. Low rumbling noises were only heard on 6 February. Crater 3 released thin white vapor gently on 9-10, 12-13, and 19 January, and during 3-4, 6-9, 14, and 16 February. No emissions were observed on other clear days. There was no seismic recording.

Langila was last reported in BGVN 28:03, following a large ash-bearing explosion on 18 January 2003. MODIS thermal alerts were subsequently recorded on 9 April and 20, 23, 25, and 27 January 2004. One daylight alert was received and omitted (22 September 2003). Daylight alerts posted by the current algorithm are considered less reliable. No corroborative reports of activity have been received from the Rabaul Volcano Observatory or the Darwin Volcanic Ash Advisory Center (VAAC).

Activity detected by MODVOLC at Langila was minimal, with only one alert pixel for 2003 (9 April) recorded just above the detection threshold, even though activity observed during January and February 2003 included weak lava projections (BGVN 28:03). Four alert pixels were recorded for 2004, on 20 (one each on Aqua and Terra), 25, and 27 January. All were 1-pixel alerts, with the highest alert ratio on 27 January at -0.764.

A thorough search of MODIS image data (i.e. original data, rather than the thresholded alert data on the MODVOLC website) was made for the period 20 May-25 October 2002, which revealed single-pixel sub-threshold thermal anomalies on Langila on a total of 25 dates, strengthening the case for the quasi-continuous or intermittent activity interpreted on the basis of MODVOLC alerts (BGVN 28:01).

Data acquisition and analysis. Reports from Diego Coppola and David A. Rothery provided analyses of MODIS thermal alerts during 2001 and 2002 (using the MODVOLC alert-detection algorithm) extracted from the MODIS Thermal Alerts website (http://modis.hgip.hawaii.edu/) maintained by the University of Hawaii HIGP MODIS Thermal Alerts team (BGVN 28:01). Rothery and Charlotte Saunders provided updates to 31 May 2004. MODVOLC data are now routinely available from the Aqua satellite (equator crossing times 0230 and 1430 local time) in addition to the original Terra satellite (equator crossing times 1030 and 2230 local time).

Langila was last reported on in BGVN 29:06, as part of a MODIS data summary, although the last prominent event there was on 18 January 2003, when a large explosion produced a thick dark ash column that penetrated the weather clouds over the summit area (BGVN 28:03).

A plume from Langila was visible on satellite imagery on 17 December 2004 according to the Darwin VAAC. The plume reached an unknown height and extended NW.

Between 28 April 2005 and 4 May 2005 the Rabaul Volcano Observatory (RVO) received reports of activity at Langila characterized by forceful emissions of thick white to gray ash-laden clouds rising ~ 700-800 m above the summit crater. Occasional continuous rumbling and explosive noises were heard and incandescence was visible at night. During early May, incandescent lava fragments were ejected. Activity increased at about 1300 on 4 May 2005, when white-to-gray ash emissions changed to dark ash clouds. Explosions became frequent, with incandescent lava fragments ejected again, and very bright glow was visible during the night. Around 1200 on 5 May 2005 the color of the ash emissions changed from dark gray to white-to-gray. A lava flow was produced but no further detail is available. Based on information from RVO, the Darwin VAAC reported that ash emissions from Langila rose to ~ 2.1 km altitude on 3 May. A very small plume and a hot spot were visible on satellite imagery. Ash clouds from the eruption were blown generally NW towards Kilenge ~ 100 km away, where light to moderate ashfall was reported.

According to the Darwin VAAC, low-level ash plumes emitted from Langila were visible on satellite imagery during 8-13 June 2005. RVO reported to the Darwin VAAC that moderate eruptive activity was expected to continue.

The International Federation of Red Cross and Red Crescent Societies (IFRC) reported that eruptive activity occurred at Langila on 2 June with more ash than normal being emitted from the volcano. Prevailing winds carried most of the initial ashfall to the sea, but lower-level winds redirected the ash back onto the island. About 10,000 people live near the volcano, and there were reports of increased cases of respiratory problems and eye irritation. During an aerial inspection of the area on 6 June 2005, IFRC determined that ~ 3,490 people had been affected by the eruption, mainly in the villages of Aitavala, Masele, Kilenge, Ongaea, Potne, and Sumel, but also to a lesser extent in Vem, Galegale, Tauale, and Laut. Ashfall damaged small food gardens and contaminated some water sources. The provincial government encouraged voluntary evacuation of affected areas.

During 16-17 June 2005, ash plumes from Langila were visible on satellite imagery (figure 4). The heights of the plumes were not reported.

Figure 4. On 21 June 2005 the Moderate Resolution Imaging Spectroradiometer (MODIS), flying on NASA's Aqua satellite, captured this image of Langila, Ulawun, and Rabaul. At the time MODIS captured this image, Langila showed the biggest plume of volcanic ash, followed by Ulawun. In all cases, winds pushed the ash clouds NW over the ocean. NASA image courtesy Jesse Allen, based on data from the MODIS Rapid Response Team at NASA.

The Darwin VAAC issued an activity report stating that the Rabaul Volcano Observatory (RVO) had noted elevated activity since 24 April 2005. Between 28 April 2005 and 4 May 2005 Langila emitted more ash than normal, and the International Federation of Red Cross And Red Crescent Societies (IFRC) determined that ~ 3,490 people had been affected by the eruption when ashfall damaged small food gardens and contaminated some water sources.

VAAC reports on 4 May and 6-7 May noted thin plumes extending NW 110 km and 75 km, respectively. Later, on 7-8 May, the identifiable plume was half as long and diminishing. Plumes and other diagnostics eventually became obscured by weather clouds. On 8 June analysts at the Darwin VAAC saw a low-altitude plume and a hot spot. The plume moved westward and remained visible into 9 June when it ceased being detectible.

During 13-19 June 2005, Langila's Crater 2 continued to erupt. At times the eruption was marked by moderate to strong emissions of thick gray-brown ash clouds occurring at irregular intervals. Ash clouds from the eruption rose variably to 700-1000 m before they were blown to the W and NW. At other times weak to moderate emissions of light gray ash clouds were observed. Considerable ash fell near the volcano and extended to the W and NW, between Warimo and Aimola. Crater 3 was quiet. Low and high frequency earthquakes and volcanic tremor were recorded.

The Darwin VAAC reported a Langila plume on 13 June to 3-4 km altitude, but cloud cover later obscured the plume. Another plume became visible on imagery on 16 June moving W at 30 km/hour at an estimated altitude of ~ 3 km; ongoing plumes became hard to see about mid-day on 17 June. Several other episodes of plume image detection were seen. One was identified by the VAAC on 21 June, with an observation of altitude to ~ 3 km and plume length reaching 300 km to the NW. The evidence of eruption only continued until the next day, when cloud cover obscured the area. A further, brief episode of plume detection occurred beginning early on 25 June but detection ended before noon. On 30 June, the Darwin VAAC repeated a US Air Force Weather Agency (AFWA) report on a Langila plume seen on imagery, blowing SW at 20 km/hr and reaching ~ 3 km altitude. By about 6 hours later that plume ceased to be visible.

Moderate levels of volcanic activity occurred at Langila's Crater 2 during 15-21 August. The activity was marked by occasional sub-continuous forceful emissions of ash clouds. The ash clouds rose as high as 1 km before drifting N and NW. Fine ash fell in villages along the coast. On the evening of 18 August projections of incandescent lava fragments were seen. Based on a pilot report, the Darwin VAAC reported that ash from Langila was visible in the vicinity of the volcano on 23 August, at 3-4.6 km altitude. A plume was seen a bit later on MODIS imagery extending 110 km to the NNW but ash was not visible in satellite imagery.

Rabaul Volcano Observatory (RVO) reported that during 22-28 August 2005, modest eruptive activity was observed at Langila's Crater 2. Occasional forceful emissions of ash produced plumes that rose ~ 1 km above the crater on 22 and 25 August, but reached only several hundred meters after that. The ash plumes drifted N and NW, resulting in fine ashfall in downwind areas, including the town of Kilenge. Seismicity was at low levels, consisting mainly of low-frequency earthquakes. The Darwin Volcanic Ash Advisory Centre (VAAC) reported that a plume was visible on satellite imagery on 30 August extending NNW.

During 12-18 September, Crater 2 continued to forcefully erupt ash at irregular intervals. The resultant ash plumes drifted NW and W. Incandescence and weak projections of volcanic material were visible on the evening of 13 September. There was no activity at Crater 3. Seismicity was at low levels at the volcano, consisting mainly of low-frequency earthquakes.

During 20-23 October, low-level plumes from Langila were occasionally visible on satellite imagery. On 29 October, a plume from Langila was visible on satellite imagery at an altitude of ~ 2.7 km.

During 11-12 November, low-level ash plumes emitted from Langila were visible. The heights of the plumes were not reported.

Vulcanian eruptions continued at Langila's Crater 2 during 21-27 November 2005, with a slight increase in the level of activity compared to the previous week. The increase in activity was marked by light to dark gray ash emissions that sometimes rose to heights between 1 and 2 km above the summit crater (7,650-10,900 feet altitude). The ash clouds drifted W, SW, SE, and NW, depositing ash in those areas. Incandescence and projections of volcanic material were visible at the volcano during the nights of 21, 23, and 25-27 November along with weak to loud noises. Crater 3 was quiet during the report period. Seismicity was at low-to-moderate levels, consisting of low-frequency earthquakes associated with the Vulcanian activity and periodic volcanic tremor.

A slight increase in vulcanian activity occurred at Langila's Crater 2 during 1-15 January. The increase was characterized by nearly continuous ash emissions that rose to 1-2 km above the summit (7,650-10,900 feet altitude) and drifted WSW. Occasionally during the report period observers noted loud noises, incandescence, and weak emissions of glowing lava fragments.
Crater 3 continued to be quiet during this period.

Moderate activity took place at Langila during January 2006, including continuous ash fall, rumbling, and weak emissions of lava fragments. During 20 January to 7 February eruptive activity was characterized by thin, pale gray ash clouds. Minimal noises were heard on 26-27 February. A changing weak-to-bright glow accompanied by projections of glowing lava fragments were visible on the nights of 22-23 and 28 February, and 1-2, and 6 March. Moderate-to-thick dark gray ash clouds were reported on 1-2, 6-7, and 9 March. Ash plumes rose less than 2 km above the summit crater before drifting SW-W of the volcano. Crater 3 remained quiet.

Moderate activity occurred at Langila between January and March 2006 (BGVN 31:05), with eruptive activity accompanied by a continuous ashfall, rumbling, and weak emissions of lava fragments. Since March 2006, activity has continued at Crater 2.

According to the Darwin Volcanic Ash Advisory Center (VAAC), eruptions at Crater 2 occurred in August 2006 and from October 2006 through March 2007, with explosions of incandescent lava fragments, roaring noises at regular intervals, and continuous emissions of gray-to-brown ash plumes. Plumes generally reached 2.3-3.3 km altitude, although on 31 October a small ash plume rose to an altitude of 4.6 km. Ash plumes were occasionally visible on satellite imagery. During October and through the first part of January 2007, plumes generally drifted N, NW, W, WNW, and NE; between the end of January and March, plumes drifted SE and SW.

Thermal anomalies detected by MODIS instruments on the Terra and Aqua satellites were absent after 2 January 2006 until 21 July 2006. The same system (the HIGP Thermal Alerts System) identified anomalies again on 24 and 31 October, 12 and 21 November, 16 and 27 December 2006, 6 January, 8 March, and 18 March 2007.

Satellite thermal anomalies occurred at or near Langila on three different days in early 2007 (BGVN 32:02). Although erupting regularly, only one other anomaly (on 2 April 2007) was detected after that time through 6 March 2008. Langila is noted for its ongoing fluctuating eruptions and occasional ash clouds that rise to more than 5 km altitude and pose a threat to aviation. Throughout this reporting period, April 2007 to January 2008, ash emissions were usually accompanied by weak to moderately loud roaring.

During May 2007, the Rabaul Volcanic Observatory (RVO) reported the emission of ash clouds from Langila's Crater 2. Ash plumes rose to an altitude of 3.3-4.3 km and drifted NW. Weak roaring noises were heard on 11-12 May and a weak glow was visible on 7-8, 11-12, and 15 May. Weak roaring noises were again heard on 20 May, and an increased phase of eruptive activity that began on 22 May continued until end of the month. The increased activity was characterized by forceful emission of thick pale-gray to dark gray-brown ash clouds from 22-27 May. The emission changed to subcontinuous thick dark gray-brown ash clouds on 28-29 May before changing back to occasional thick, pale-gray clouds on 30-31 May. Two large explosions on 30 May accompanied the ash emission. The ash clouds from these two explosions rose 4 km above the summit before being blown NW. On the other days, the ash clouds rose 2-3 km above the summit before drifting NW of the volcano. Continuous fine ashfall occurred at Kilenge Catholic Mission (~10 km NW) and surrounding areas during 22-31 May. The ash emissions were accompanied by occasional weak to loud roaring noises from the 22 to 28 May before turning subcontinuous during 29-31 May. On 30 May two large explosions produced ash plumes that rose to ~5.3 km and drifted NW. A weak glow was visible on 7-8, 11-12, 15, and 20 May and again on 29 and 31 May. Incandescence was visible on 29 May. On 26 May, the seismograph deployed at Kilenge became operational.

During June RVO reported a slight decrease in eruptive activity that began on 22 May, however, the emissions of ash plumes from Crater 2 were occasionally forceful. The emissions were continuous on 6, 7, and 10 June and accompanied by roaring noises; booming noises were heard on 1 and 10 June. Ash plumes rose to ~ 2.3-4.3 km and drifted NNW. Based on observations of satellite imagery and information from RVO, the Darwin VAAC reported that on 3 June, an ash plume rose to an altitude of 3 km and drifted W. Ashfall was again reported at Kilenge Catholic Mission and surrounding areas. Seismic activity in June was at a high level, dominated by continuous tremor and occasional explosion signals. During the latter part of the month, seismic activity decreased to a low-moderate level. It was dominated by continuous irregular tremors and occasional harmonic tremors. Low-frequency earthquakes ranged from 1 to 7 events per day.

During July 2007, eruptive activity continued at a low level but included thin-to-thick, pale-gray ash clouds. Weak roaring noises were heard on 1 July, but glow was absent at night. On 2 July ash clouds were ejected forcefully and rose ~2 km, drifted NW, and resulted in a fine ashfall downwind. On 6-7, and 9-13 July, ash clouds rose less than 1 km above the summit before drifting NNW. Except for 1 July when weak roaring noises were heard, the volcano was quiet and without appreciable night glow. Seismicity registered at low-moderate levels, dominated by non-harmonic and harmonic tremor of continuous, irregular, or banded character. During July, the daily number of low-frequency earthquakes ranged between 1 and 12 events per day. The one high-frequency earthquake occurred on 27 July.

RVO reports noted mild but continuous ash and white vapor plumes from Crater 2 during 1 August-30 September. Ash plumes generally rose to altitudes of ~1.8-3.3 km and drifted WNW. On 8 August, a large explosion produced an ash plume that rose to an altitude of 5.3 km and drifted SW. Ashfall was reported downwind. Incandescent fragments were ejected from the summit on 21-22 September.

During 1-7 October 2007, RVO reported low-to-moderate eruptive activity consisting of continuous emission of pale gray ash clouds which rose to ~1.8-3.3 km and were blown W to NW. During the second week, the white vapor accompanied by pale gray ash clouds continued; these rose less than 1 km before being blown to the NW of the volcano. On 19, 16, and 27 October, the ash clouds rose less than 2 km before being blown WNW. Consistently, the ash emissions were accompanied by occasional weak-to-loud roaring or booming noises.
On most occasions, there was no glow observed at night, however, a weak-to-bright glow accompanied by projection of incandescent lava fragments was visible on 12 and 22 October. Crater 3 remained quiet. Seismic activity was at low-to- moderate level dominated by low frequency earthquakes and bands of harmonic and non-harmonic tremors. The daily number of low-frequency earthquakes ranged from 2-15. Less than 10 high-frequency events were recorded during October.

In January 2008, activity generally remained low. Some ash fell on 6-7, and 9 January with fluctuating glow visible. On 10, 13, and 25 January the incandescent glow was bright. More direct observations through late February 2008 by RVO staff and affiliates confirmed ongoing eruptions. During February, Crater 2 continued to erupt. Most days, these eruptions generated ash plumes typically rising a few hundred meters. Observers noted incandescent glow or noises on 7, 9, 11, and 21-23 February.

Although the Rabaul Volcano Observatory (RVO) reported ash eruptions and glow as late as 23 February 2008 (BGVN 33:02), subsequent available reports did not include Langila until July 2008. That report noted weak emissions of light gray ash clouds during 1-6 July, followed by white vapor for the remainder of the month, with no glow observed. Activity at Langila was again not described in available observatory reports until September 2009, and thermal anomalies were noted in early October 2009.

Vulcanian activity occurred from Crater 2 throughout September and the first week of October. From the beginning of September emissions consisted of light brown to dense pale white/gray ash clouds that rose 800-1,000 m above the crater rim. Occasional roaring and rumbling noises were heard. This eruptive episode produced significant amounts of ash, primarily affecting areas NW, W, and SW of the volcano.

Stronger activity during 20-24 September consisted of dense dark gray ash clouds and some incandescent ejections. Plumes rose 2,000-3,000 m above the rim during this period. The emissions also produced continuous roaring noises and booming explosion sounds. Some lightning discharges accompanied the explosions. GNS of New Zealand and the Darwin VAAC detected very strong airborne sulfur dioxide (SO2) in satellite data on 26 September. On-site observations did not indicate strong activity that day, so it was thought to have been from the 20-24 September activity.

Emissions subsided on 25 September to the previous level, and continued during the first week of October, then declined to continuous white-gray ash clouds. This type of activity, with plume heights around 600 m, continued with minor variations until the end of October. The audible noises declined to occasional weak roaring after the first week of October. Night-time glow was also visible throughout September and October.

Some plumes during this episode extended great distances downwind, prompting aviation warnings. Based on analyses of satellite imagery, the Darwin VAAC reported that on 12 September an ash plume rose to an altitude of 3 km and drifted 35 km W. On 29 September ash plumes rose to altitudes of 2.4-4.3 km and drifted 75-220 km NW. Another ash plume the next day drifted 260 km NW at an altitude of 4.3 km. A diffuse ash plume on 5 October rose to an altitude of 3 km and drifted 185 km N.

Thermal anomalies identified in MODIS data were recorded on 10, 22, and 26 September, and 5-6 October. MODVOLC alert pixels appeared to be located outside of the crater on the ENE slope.

In September 2009 eruptions occurred at Langila's Crater 2, sending aloft dense ash plumes seen for hundreds of kilometers. Activity subsided but continued as late as the end of October 2009 (BGVN 34:11). Later reports from the Rabaul Volcano Observatory noted activity at Langila in December 2009 and February 2010. No MODVOC thermal alerts were recorded after 5-6 October 2009, through February 2010.

Vulcanian eruptive activity continued at Crater 2 throughout December 2009. The eruptive activity consisted of variable gray ash clouds on most days of the month that rose ~ 1 km above the summit before being blown NE, causing fine ashfall downwind.

During 11-15 February 2010 observers saw weak ash plumes from Crater 2. During the latter part of the month the plumes were stronger, rising 700-900 m above the crater and drifting SE and SW. During 15-19 February observers heard occasional weak booming noises.

Geological Background

Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Synonyms

Langla | Nangila | Nanla

Cones

Feature Name

Feature Type

Elevation

Latitude

Longitude

Angila

Cone

1080 m

5° 33' 0" S

148° 26' 0" E

Gulu
Bulu

Cone

1093 m

5° 32' 0" S

148° 26' 0" E

Munlulu, Mount

Cone

1040 m

5° 33' 0" S

148° 25' 0" E

Talawe, Mount
Below, Mount

Stratovolcano

1824 m

5° 32' 0" S

148° 23' 31" E

Craters

Feature Name

Feature Type

Elevation

Latitude

Longitude

Chimney Crater

Crater

5° 32' 0" S

148° 25' 0" E

Fissure Crater

Crater

5° 32' 0" S

148° 25' 0" E

Munlulu

Crater

1200 m

5° 32' 0" S

148° 25' 0" E

Twin Crater

Crater

5° 32' 0" S

148° 25' 0" E

Photo Gallery

Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite cones on the lower eastern flank of the extinct Talawe volcano. Steam rises on September 4 from Craters 2 (left) and 3 (right) during a 1970 eruption. The rim of Crater 1 forms the center horizon in this view from the NW. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from the three active craters at the summit of Langila.

Photo by Wally Johnson, 1970 (Australia Bureau of Mineral Resources).

References

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.

EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).